The numbers I've seen excludes on-line sales, which I suppose includes Steam, so the numbers could be very different.
On-line sales are almost never included in sales charts. Particularly Steam, as Valve never releases sales figures. Steam has grown into a behemoth though, considering it's popularity.
And this is one of the things that we can thank consoles for: A new computer bought 2-3 years ago can still run new games. A decade ago you could forget about trying to run a new game on a computer that old.
And you could also curse at the consoles for that. PC gaming is dirt-cheap these days. But because the consoles limit progression in game-design, like graphics, most games have very little improvement to offer for people who've got higher end gaming rigs.
So, that you can run vanilla Skyrim maxed (maxed+ actually with texture replacers, upped .ini settings, etc) on a Core2Duo with a 1st gen GTX460 is both a blessing and a curse imho.
Except you can't see that rabit out in the distance on the tiny, non-HD screen. "I can't hunt like this" you say to yourself. Time to get a 42-inch HD flat screen. 500 bucks. All said and done, you could easily drop 2000-2500 dollars on a killer gaming machine.
1080p 21"-23" monitors can be bought dirt-cheap these days. With more then acceptable gaming performance (refresh rates, input lag, color accuracy, black to grey shading).
Given the distance you're at while playing on PC (if you play on PC sitting at a desk), 21"-23" is more than big enough for a 1080p monitor.
And most people will have something like a 42" 1080p LCD/Plasma in their home anyway these days (or be looking to get one), which off course won't be solely used for gaming.



