Earlier today Forbes published an article on Valve, calling Gabe Newell the next gaming billionaire, if he's not one already. Forbes estimates Valve's value at $2-$4 billion, with Gabe Newell owning over half of the completely privately owned company. The article goes on to mention that Half-LIfe 2 has sold more than 12 million copies, and, perhaps most shockingly, Gabe Newell claims Valve makes more money per employee than Google or Apple. Since Google and Apple are publicly traded companies, their ratio of profit per employee is no secret, so there's really no way the PC software tycoon could be wrong.
Valve's primary profit machine, Steam, easily the largest digital distribution service on PC (and arguably on any platform), was estimated by Forbes to have earned an astounding $1-$2 billion last year. There is no way to directly confirm these estimates, as Valve is infamously private about the sales of Steam software, but it's hard to argue with that kind of success. These estimates on the value of Valve and their revenue would put the independant company well out of the range of purchasability from even the largest of third party publishers, such as EA. With many gamers (and even some publishers) still claiming PC gaming is dying, this news may change some opinions on the subject of PC's viability as a major gaming platform.
You can find the full article on Forbes, linked below.