But instead of hitting each provider's API separately, managing their keys, etc., it may be easier to go through OpenRouter, which is a single endpoint, has hundreds of models, and doesn't add any cost on top of public prices from the providers.
You buy credits on OpenRouter, or rather you load money onto your account and then as you make API calls your account balance is deducted by the cost displayed on OpenRouter's website (market rates).
So once money is loaded on your account you pay the same as if you used the LLM provider directly but you pay a premium to load money onto your account, it's effectively adding a 5% fee to the base LLM API prices (and $0.35/per reload, depending on reload amount this might be negligible but on a $10 reload it means you are effectively paying a 9% fee).
They charge you a service fee (5% + $0.35) when you reload credits. This is very well hidden and not publicly stated (or at least I couldn’t find it would logging in and trying to purchase).
But instead of hitting each provider's API separately, managing their keys, etc., it may be easier to go through OpenRouter, which is a single endpoint, has hundreds of models, and doesn't add any cost on top of public prices from the providers.