You are not mistaken - the $600 PC's are typically appliances that do web/email, but certainly not high-end games. A Good graphics GPU today could run you $250-$300 bucks all by itself.
I would expect that a modern PC with a good monitor, 4Gigs mem, 1T of disk and a modern GPU would run at least $$1200 at a minimum for a good system. Add an SSD drive and shoot for top-end GPU and CPU, then $1500-$2000 is more realistic.
I build all my systems component-wise from stuff I buy at NewEgg so I'm used to the prices. There is still a huge price difference between a Strong PC and a PS/3, even at the old PS/3 prices.
My latest system cost $1600 and has 13 GB of RAM (12 GB system, and nearly 1 GB on a GTX 260 Nvidia card), plus a 1 TB harddrive and an 2.6 ghz i7 Quad-core CPU. All water-cooled. And that is straight from Dell, not something I put together from discount parts from Newegg (which I have done in the past for pretty cheap as well). Sure that's 2 or 3 times the price of a console, but factor in not having to buy extra controllers at $50 or $60 a pop, and paying $10 less for every new game, or less compared to console releases, it pays for the difference in a couple of years, especially if you use the PC for other things besides gaming, like watching Blu-ray movies or making 3d graphics.
Not to mention that my system is probably drastic overkill for most games at the moment, especially New Vegas so you could spend hundreds of dollars less and still get a system that ran New Vegas maxed out (if it is anything like FO3). Like I previously mentioned, I played FO3 originally on a 7 year old system. I had to keep the settings on Low, but it ran smooth and I was even able to use quite a few mods.
The Gamebryo engine isn't that demanding if you have a decent amount of RAM. (My old system had 2 GB, plus a 256 MB card.)
Just food for thought.