A few things you said that made me kinda laugh a little bit:
Consoles DO NOT cost about as much as a good PC. The most expensive popular console out there right now is $200 USD. Find me a good computer for $200, and I'll become your wife.

Even if I have to buy a new console after 2-3 years, it STILL costs less than buying a new computer, or a bunch of new hardware. Easier to install, too, as there is no installation Games still cost the same, and thanks to backward compatibility, consoles are able to handle a wider array of games.

Yes, I know computers are also evolving. Most things do: it's called "the passage of time." However, the one thing that isn't evolving right now is the size of my bank account.

I'm not saying "don't buy computers for games." I'm saying "this is why people buy consoles," which is the exact question you asked.

Match point: (antihero)
*crowd goes wild*