That doesn't surprise me in the least. you might want to read this: http://danluu.com/startup-tradeoffs/

Dan Luu's numbers are very conservative - keep in mind that the kind of people who get hired at Valve are far above the bar that Dan Luu sets for the "not particularly unsuccessful" senior engineer.

Not really surprising considering their bar to hire.

I've worked with a couple of ex/current Valve people, they're effing sharp/creative.

But it seems to be more lucrative than a hedge fund.