At 10,000 users Clerk was free. At 50,000 users our bill was $800/month. At 100,000 it would have been $1,825/month. We switched to Supabase Auth and now pay $25/month for the same functionality. Here is how the math works and when Clerk is still worth it.
The Auth Provider Pricing Nobody Talks About
Every auth provider has a "free tier" that makes them look cheap on the pricing page. The real cost emerges at scale. At 100K monthly active users:
| Provider | Free MAU | Per MAU after | 50K MAU | 100K MAU |
|---|---|---|---|---|
| Supabase AuthCHEAPEST | 50,000 | $0.00325 | $0 | $25 |
| Firebase Auth | 50,000 | $0.0055 | $0 | $275 |
| Clerk | 10,000 | $0.02 | $800 | $1,825 |
| Auth0 (Okta) | 7,500 | $0.07 | $2,975 | $5,000+ |
Same authentication. Same JWT sessions. Same social providers. The 73x price difference is purely a per-MAU billing model decision.
Why Clerk Gets Expensive Fast
Clerk's $0.02/MAU rate sounds tiny. Then you do the math: 100,000 users × $0.02 = $2,000. Minus the 10,000 free MAU allowance = $1,800. Plus the $25 base plan fee = $1,825/month.
The inflection point is brutal. At 9,999 MAU: $0. At 10,001 MAU: $0.02. Growth from 10K to 100K means your auth bill goes from $0 to $1,800. Most SaaS products don't notice until they're already at 50K+ users.
Clerk is free under 10K MAU. Once you cross that threshold, you are paying $0.02/user/month on every user above 10K. At 50K users that is $800/month. At 100K that is $1,825/month.
Supabase Auth: What You Give Up
Supabase Auth does not have Clerk's polished pre-built components. There is no drag-and-drop sign-in modal. You build login UI with their SDK. For teams already using Supabase for their database, this is a non-issue — the SDK integrates naturally. For teams starting fresh, Clerk's DX advantage is real and worth paying for until you hit scale.
When to Choose Each Provider
| Situation | Recommendation | Reason |
|---|---|---|
| Early stage, under 10K MAU | Clerk | Free + best DX |
| Using Supabase DB already | Supabase Auth | Essentially free, native integration |
| Growing past 50K MAU | Supabase Auth or Firebase | Clerk becomes $800+/mo |
| Enterprise B2B with SSO | WorkOS | 1M MAU free, SSO-first |
| Complex compliance (HIPAA, SOC2) | Auth0 | Compliance-first, expensive |
Calculate your auth cost at your current and projected MAU
Calculate My Auth Cost →Supabase Auth is the cheapest at scale: 50,000 free MAUs then $0.00325/MAU. At 100K users it costs ~$25/month. If you are already using Supabase for your database, auth is essentially free.
Clerk wins for developer experience and Next.js/React apps. Auth0 wins for enterprise compliance, SAML SSO, and complex B2B requirements.
Moderately difficult. You need to export users, recreate social provider connections, and rebuild any pre-built Clerk UI components. Budget 1-3 days depending on your app complexity.