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Walkthrough: My process for evaluating AI coding assistants

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(@cost_optimizer_88)
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Joined: 3 months ago
Posts: 95
Topic starter   [#8551]

Alright, let's get this out of the way upfront: I'm here because I'm tired of watching teams hemorrhage cash on the latest "productivity multipliers" without ever calculating the ROI. You'll find me mostly in the FinOps and Cloud Cost subforums, dissecting someone's poorly-architected Kubernetes spend or explaining, for the hundredth time, why buying a 3-year reserved instance for a stateless workload is financial malpractice.

My vertical is consulting, specifically pulling distressed projects out of financial quicksand, which usually involves a combination of cloud waste, over-provisioning, and a pathological fear of committing to any long-term spend even when it's screamingly obvious.

I've been evaluating AI coding assistants—GitHub Copilot, Cursor, Amazon Q, etc.—not as a starry-eyed developer, but as a cost optimizer. My process mirrors how I evaluate any service with a recurring fee: I treat it like a cloud resource.

Here's my framework:

1. **Establish the Baseline:** I don't care about "lines of code" or "time saved" in the abstract. I start with the fully-loaded cost of a developer-hour for the team in question. If that's $120/hour, and an assistant claims to save 10% of time, it needs to justify `($120 * 0.10 * developer_hours_per_month) > (assistant_monthly_fee * number_of_developers)`. Most teams skip this and just expense it.

2. **Identify the Instance Type:** Is this a "spot instance" (unreliable, context-drops, but cheap for brainstorming) or a "reserved instance" (deep, consistent, context-aware completion)? The pricing models often don't align. A tool like Cursor, with its deep IDE integration, is a committed use discount; a ChatGPT Plus tab is on-demand, interruptible, and often more expensive per meaningful output.

3. **Rightsizing the License Tier:** Vendors love to upsell to the "Pro" tier with "enterprise features." I map features to actual, measured needs.
* Is the codebase index/context window providing tangible completion accuracy, or is it just a vanity metric?
* Are the "advanced" chat modes being used for daily work, or are they a novelty that wears off after week two?
* I'll often recommend a mixed strategy: a few "reserved" Pro seats for leads/architects doing deep design work, and "spot" standard seats for the general dev team.

4. **The True Test: The Burn-down:** I run a one-month pilot with a small team, but I don't just ask for feelings. I instrument it.
```python
# Pseudocode for a simplistic but revealing metric
cost_of_assistants_this_month = (seats * monthly_fee)
estimated_dev_time_saved = sum(assistant_logged_events * average_time_per_task)
monetary_value_of_saved_time = estimated_dev_time_saved * dev_hourly_rate
ROI_ratio = monetary_value_of_saved_time / cost_of_assistants_this_month
```
If `ROI_ratio < 1.5`, the case for rollout is weak. You need a buffer for diminishing returns and management overhead.

What I'm hoping to find here are posts from others who think in terms of unit economics, not just cool features. I want deep dives into the actual, measurable throughput changes from these tools, horror stories about vendor lock-in with proprietary context layers, and clever hacks to get 90% of the value for 50% of the price.

I'll contribute breakdowns of pricing models, analyses of when it's cheaper to run a fine-tuned open-source model internally (and when it's catastrophically expensive), and probably a few sardonic takedowns of the next "AI-powered" tool that wants $50/head/month without a clear path to payback.


pay for what you use, not what you reserve


   
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