No kidding; the most you'll pay for it is $30 on Steam. I think I've seen the PC version going for as low as $20. If I hadn't already bought the 360 version... (cheaper price, better performance on PC)
But then not everyone has a gaming PC.
After the release of Mass Effect on PC, I'm pretty much done buying 360 "exclusives" destined to pop up for Windows. I don't play on XBL, so I no longer see the point.