How many packets per second will a pi route?

From professional experience, I can tell you that the average routing hardware (typical OpenWrt routers) will not be sufficient to actually handle the load from only a few dozen users sharing a simple DSL connection.

I've resorted to mikrotik hardware for that reason. You might want to have a look at their stuff, just a suggestion.


Edit: also, maybe if you just setup the pi as a RADIUS server, you could enable bitcoin payments for practically all the generic hotspot solutions on the market.