1/3 is overstating the case. A lot of it is because Macs all include hardware that I couldn't care less about.
Let's take their cheapest offering, the
$599 mac mini. Intel i5 2.5 ghz dual core, 500 GB hard drive, Intel HD graphics, 4 GB ram. This
combo from newegg has better graphics (caveat: not familiar enough with intel HD graphics to be certain on this point, but I'd bet it's at least comparable), better hard drive, better processor for $303. Call it $403 once you add windows, so about 2/3. That's not necessarily the best one to use for comparison, just the first I came to.
This one for instance is another $100, with a better processor and builtin graphics. If you don't think that qualifies as a gaming rig, throw on an actual graphics card to either combo and disable the onboard video.Might not be top end, but it should cover your gaming needs.