Earlier quoted context omitted.
30% off the top for most stores (Valve/Steam, Apple/iPhone, Google/Android, etc), then around 50% taxes between state, local... some fixed expenses and overhead. It's probably well under 20% in the bank after all is said and done. That said, it's still a lot of money.
God, that's awful. That 30% cut for the middle man hurts. At least the government tax can be put to good use (emphasis on can ...)
Generally, the Steam cut is considered “fair” for Indy devs. The benefits of steam (discoverability, massive audience) generate more sales. My Indy dev friends are not upset about the steam cut at all.
This, however, is one area where eventually Epic Games shines — they take a much lower cut and if they increase in popularity with gamers then steam might be forced to lower their share.