Would you use funded keys for your SaaS Apps?

Hello everyone, I wanted to gather some feedback on a new authentication strategy called Funded Keys that I have recently implemented in my SaaS app. Funded Keys deviate from traditional authentication methods by allowing users to fund a key, similar to developer API keys, which enables usage tracking and monetization. This approach is particularly suitable for straightforward apps that necessitate user tracking while bypassing the need to build a complete authentication flow. What are your thoughts and opinions on this approach.