I think it's pretty safe to assume that all their own game revenue is dwarfed by the 30% steam cut they take on the sales of everyone else's games.
And then the asinine fees to sell an item to another player...
And then the asinine fees they take for community map rotations...
And then the asinine fees they take for community skins and items...
It's both amazing and disgusting how much money Valve makes from their little value-add services.