These are private computers for gaming with Steam installed. This will literally be less than pocket change to them. They likely lose more from pirated Windows and secondhand purchasers of Apple products.

The amount of money tech giants lose will not be affected for a long time. The main achievement for Linux right now would be to get a foothold, to make it known to the public, to normalise its use. The big change will come when organisations start moving to Linux (which you would think would be a priority considering the fact that it is free and more secure).