Alright, let's cut through the marketing. Everyone talks about "ease of use" and "developer experience," but I'm here to talk about the invoice. Specifically, what does it actually cost to run Auth0 versus rolling your own with AWS Cognito for a mid-sized application?
I'm defining "mid-sized" as 50,000 Monthly Active Users (MAU). That's a real number for a real business, not some startup's fantasy. Let's assume a typical B2C SaaS pattern: social logins (Google, Facebook), email/password, and maybe one enterprise SAML connection.
**Auth0 Cost (B2C Plan, list price)**
* 0-7,500 MAU: Free (hah, a trojan horse)
* 7,501-50,000 MAU: $0.03 per MAU
* **Estimated Monthly Cost:** (50,000 - 7,500) * $0.03 = **$1,275**
* **Annual Cost:** ~$15,300
That's before any add-ons. Want custom domains, advanced anomaly detection, or more than one enterprise connection? That's extra. The price scales linearly, so at 100k MAU you're looking at ~$2,775/month.
**AWS Cognito Cost**
Cognito pricing is granular. For 50k MAU:
* MAU fee: $0.0055 per MAU for the first 50k.
* **MAU Cost:** 50,000 * $0.0055 = **$275/month**
* Social Identity Provider logins (through User Pools): $0.015 per authentication.
* Let's assume 2 logins per user per month (conservative): 100,000 auths * $0.015 = **$1,500/month**
* SAML/OIDC provider logins: $0.015 per auth (if using the enterprise IdP).
* **Estimated Total Monthly Cost:** $275 + $1,500 = **$1,775**
**Initial Observation**
The raw numbers are closer than I expected: ~$1,275 vs. ~$1,775. Auth0 looks cheaper at first glance. But this is where my skepticism kicks in.
* The Cognito estimate includes a *lot* of external auth events. If your users are less active or you use native Cognito hosted UI more, that cost drops fast.
* Auth0's cost is predictable. Cognito's is usage-based and can spike.
* The real cost is in engineering hours. Cognito is infamous for its rough edges, poor documentation, and "undifferentiated heavy lifting." How many developer sprints will you burn configuring it versus Auth0's more polished dashboard?
* What's your break-even point? If you need 2+ FTEs for a quarter to build what Auth0 gives you out-of-the-box, that's a $50k+ engineering investment. At a $500/month price delta, it would take years to justify.
I'm not sold on either yet. Has anyone actually run this at scale and done a true TCO, including support and operational overhead? I want to see real numbers from someone who's migrated from one to the other.
-auditor
Show me the bill