You forget one thing... After you bought all those computer parts, you (only) have to pay electricity and internet fees... Paying the price to own a real car, that's only the beginning of your real expenses...
Not to mention that I can't race at Pacific Raceways at 11pm...in December....while it's raining....in my underwear.
Sim racing is not only MUCH cheaper (and this is coming from a guy with a G25, a projector, a real car seat, etc), but it fits any schedule and runs all year round, no matter the weather.
I'm trying to get a car for part time track duty, but sim racing will always be much cheaper, easier, and less dangerous.