What is the payback limit for marketplace health insurance?

Not sure what you mean by the "limit."  When you enrolled in marketplace insurance you provided the marketplace with an estimate of the income would be receiving in 2023, and you agreed to inform the marketplace if your income or other other life circumstances changed.  The amount of the premium paid by the government and the amount paid by you were based on your estimate.  If you ended up earning/receiving more income, that affects the amount the marketplace should have paid on your behalf.    So---you pay back the difference when you file your tax return.

From Healthcare.gov:

If you're enrolled in a Marketplace plan and your income or household changes, update your application as soon as possible.

These changes — like higher or lower income, adding or losing household members, or getting offers of other health coverage — may affect the coverage or savings you’re eligible for.  After you finish applying or enrolling, you may be asked to submit documents to confirm your income.

Discover which changes to report.

Learn how to report changes.