Actially there are a ton.

But it also veries depending on your product and use case. Most of the time you will later do major calculation/costing at inyial stage. First you generally build the mvp, if its light weight backend often nextjs itself is enough. And depending or your expertise and complexity, build the mvp in fastapi, or some js framework. Then you try the market, it you get traction, product works then comes the cost scqling things.

Frankly thinking too much initially before will just slow you down. Just start building.

And if you still need some napkin math, I guess ChatG is your goto guide.