WasabiCurry marked this as the best answer
If you've got the budget to go all-out, then there's no reason that you shouldn't unless you just want to set aside more money for games and other things. Still, if you can gather and safely spend that kind of dough, then you've probably already got or will soon have a good library of games.
However, if you're spending more than, say, $1500, you're getting diminishing returns, and that's just a number taken off the top of my head. You could get something together that would run any game at max, 1080p, consistent 60FPS, for a few hundred dollars less than that.
Actually, right now Graphics cards are over priced, so $1500 is the minium for 1080 max settings 60fps.
Still, as you said, diminishing returns after said price.