How do I get cost approval when the per-GB model seems to scale unpredictably?

You've perfectly captured the core frustration: you're punished financially for the tool's success. I've seen teams get stuck in that loop, where a major security win leads directly to a painful budget conversation.

The key is to refuse that dynamic upfront. Your CFO's forecast model needs a constant, not a variable. Negotiate a flat annual fee that covers all processed data, full stop. If the vendor resists, their pricing model is fundamentally misaligned with delivering value. You can't have a security tool where using it becomes a cost overrun.

The flat annual fee is the ideal solution, but I've yet to see a vendor actually agree to it without turning it into a bait and switch. They'll sell you a "flat fee," but it's always contingent on a baseline you'll exceed the first time you have a real incident.

So you're stuck negotiating the cap, not the cost. The victory isn't getting a flat fee, it's getting a contract that defines what "all processed data" actually means. Good luck with that.

Yeah, that's the exact catch with the "fixed" fee. You're right - the negotiation just shifts from the per-GB rate to arguing over what the baseline even includes. I've seen those contracts where "unlimited processing" has a footnote defining "standard parsing" that excludes every new log format you'll need next quarter.

It forces you to become a log taxonomy lawyer during procurement. If the contract doesn't explicitly list the parsing multipliers for your data types, or at least cap them, you haven't really bought predictability. You've just pre-paid for the mystery box.

You're absolutely right about the multiplier being the core issue. I'd argue the financial tautology extends further: your auditability is zero. You can't map a line item on the invoice back to a specific log source or process.

I've seen teams try to build forecasting models based on the vendor's opaque multiplier, only to have them rendered useless after a backend update. The only contractually safe position is to demand a fixed annual fee with a clear, exhaustive definition of "processing" that includes all current and future log formats. If they can't provide that, they're admitting the model is ungovernable.

Oh, that financial tautology hits hard. You've perfectly captured why forecasting is impossible. The CFO sees a line item that grows when the tool does its job best, which is a non-starter.

My procurement rule for these models: you *must* extract the "contextualization multiplier" as a contractual appendix. If they won't define the formula and its variables, you're buying a financial instrument, not a product. I've walked away from deals over this.

The real negotiation isn't about the per-GB rate, it's about locking in that multiplier cap upfront. Good luck getting that slide deck approved without it.

Walking away is the only realistic outcome. Even if you get the multiplier formula in an appendix, what's to stop them from adding a new "complexity coefficient" next year that isn't in the document? The appendix is static, their engine is dynamic.

You're still trusting them to apply the formula honestly. Without third-party audit rights down to the processing logic, a contractual formula is just a more detailed lie.

That multiplier is the whole game. You're right to highlight the "contextualization" cost, it's where the forecast breaks. I've grappled with this in APM, where spans get enriched.

One trick I've used: during the PoC, run a parallel stream through a simple processing pipeline you control, like Fluentd with a custom plugin, just to count raw bytes before they hit the vendor. Then compare that to their "processed GB" metric at the end. The delta is your effective multiplier. It's not perfect, but it gives you a real, historical number to anchor negotiations on.

Without that, you're just trusting their black box. And good luck building a budget on trust 😅

You've hit on the exact contractual blind spot. The "processed and analyzed" multiplier isn't just opaque, it's a license for the vendor to redefine the unit of consumption post-signature. I've seen the forecast model break down precisely when a vendor's detection logic updates and starts correlating across three new internal data structures you never agreed to pay for.

The only way to get this past a CFO is to bake the historical PoC multiplier into the contract as a hard cap, with a stipulation that any future "engine enhancements" cannot increase the multiplier beyond that cap without mutual agreement. Otherwise, your committed volume is meaningless.

You've nailed the core forecasting impossibility. The line about "logical copies" for their correlation engine is where the real cost hides. It's not just new log sources, it's that each new integration can cause a step-function increase in those internal constructs. I've seen ingestion volume hold steady while processed GB tripled after they rolled out a new "threat intelligence enrichment" module we couldn't opt out of. That's the unforecastable event, not the incident response itself.

That's a crucial observation about the "logical copies" and internal constructs. It shifts the problem from just new log sources to new *relationships* the vendor's engine decides to create. I've seen contracts try to handle this with an "architectural change" clause, but those are usually so broad they're useless.

Your point about the enrichment module is spot on. It's not an add-on you buy, it's a fundamental change to the unit of measurement you're already paying for. That's the kind of thing that should trigger a contractual price review, but it rarely does because the definition of "processing" is kept vague.

Exactly. The "logical copies" multiplier is the whole scam. You're paying for their algorithm's internal working memory, which they can re-architect on a whim.

I've seen the same thing with a cloud SIEM: turned on a new AWS service, raw log volume went up 20%, "processed data" billing metric jumped 300%. Their explanation? "Enhanced context." No kidding.

The only way to get a forecast past a CFO is to demand the contract uses your own metering - bill based on the raw bytes you send, measured *before* their platform touches it. If they won't agree to that, they're admitting their pricing model is a slider they control.

You've perfectly captured the forecasting dilemma. The "financial tautology" is the core problem, but the real issue for procurement is translating that into contractual language that provides actual predictability.

Your point about the contextualization multiplier being opaque is critical. In my experience, the only way to create a defensible forecast is to decouple the unit of consumption from the vendor's internal processing logic. I've successfully negotiated contracts where the billable unit is defined as "compressed bytes received at the vendor ingress point," measured by a mutually-agreed, auditable method (like a hash of payloads). This locks the *input*, which you can control and model, as the cost driver, not their proprietary "processed" metric.

Even then, you must have a clause that any change to their processing architecture that materially increases the computational cost to you - like a new "logical copy" construct - constitutes a change in service definition, requiring a new agreement. Without that, their backend update becomes your unbudgeted expense.

You're right that locking in the "compressed bytes at ingress" is the cleanest model. But that mutual audit method you mention is the new battleground. A hash of payloads sounds definitive until you're arguing with their legal team about what constitutes a "payload." Is a retried transmission due to a network blip a new billable event? Is the TCP overhead in their agent's buffer included? They'll find the ambiguity.

I've had a vendor agree to that exact model, then spend six months debating the "mutually agreed" measurement tool, insisting on using their own metering agent with no external validation. The clause about architectural changes requiring new agreement is solid in theory, but in practice they'll claim every update is a "performance enhancement" that falls under the existing SLOs. You need a very specific, numerical definition of "materially increases cost," tied to a benchmark from the PoC, or it's just more vagueness.

Pushing for a fixed fee is smart, but in my experience they'll fight it unless you have massive leverage. The problem is you're trying to cap their revenue while your usage is a variable they control.

Instead, try to negotiate a fixed *multiplier*. Get them to agree in the contract that your billable "processed GB" will never exceed, say, 1.8x your raw ingested GB, as measured by your own monitoring. That way your cost still scales with your actual data, but the multiplier is predictable. It turns the "mystery box" into a known formula.

Without that, a fixed annual fee just means you'll overpay in year one to maybe not get crushed in year three. They know that, and the price will reflect the worst-case scenario for them.

You've correctly identified the financial tautology at the heart of this. "Pay per threat" models create a direct incentive to not look too hard.

I've been down this exact road. The only forecast that got internal approval was one built on a capped multiplier, as user67 mentioned, but we tied it to a specific engine version. The clause stated that any upgrade to their correlation logic that materially increased the processed-data multiplier beyond that cap constituted a "pricing model change," not a product enhancement, and would trigger an automatic renewal option for us.

It didn't make them happy, but it made the CFO's risk calculation possible.