usage_credits

https://github.com/rameerez/usage_credits

Add a usage-based credit system to your Rails app, easily. Let users buy and spend credits on usage-based actions. Refill Stripe subscriptions with credits, sell one-time booster credit packs, implement PAYG (pay-as-you-go) billing, award free credits as bonuses, manage prepaid credits / tokens. Your users will have wallet balances that they can spend on features, API calls, or other usage-based actions. Perfect for SaaS, AI apps, games, and API products with metered pricing / billing.