Small nitpick: AIUI it is possible to sell binaries of a GPLv2 program, provided you keep providing source for free. (I think; IANAL, there's maybe some caveat about exactly when you have to give source and to who.) That can actually work if your users don't want to compile stuff themselves.
In theory. Show me one example (not service or support, but selling actual software). You have a better chance of winning a lottery, happens every day.
In theory, I can just walk through solid wall, using a quantum tunneling effect.
The closes thing you will find are things like blender release under GPL (i.e. pay me a money to release my commercial software under GPL, but that's not selling GPL software),
