Something I'd probably do is make a very basic app (e.g. 'todo' app) in each framework, deploy all 3 to heroku, and check out the 'metrics' tab. For a few hours' work, that should give a rough idea of CPU and memory, at least for a very small app.

One other thing:

> I want to spend as few dollars on hardware as possible.

This is a perfectly sensible objective, but always keep in mind any trade offs between development time and server costs. Sometimes less efficient frameworks are faster to develop in, and it can be worth suffering a slightly greater server bill to get an MVP out quickly, especially if the server bill is small to begin with.