an expensive CPU does _not_ bring you a sizeable benefit in gaming performance. Very poor bang for buck.
Versus what? An i5, a quad without hyperthreading? You're right, except if you want to do something like stream your gaming on Twitch or record it to your hard drive with OBS. In that case, an i7 is essential, the hyperthreading has a benefit that far exceeds the cost to go from an i5 to an i7.
I think the i7 is worth the extra cost compared to what else I could spend the extra $100 on. But its true that if I'm playing a benchmark instead of playing (and simultaneously recording/streaming) a game, it won't show any benefit there.
If you're talking about the Extreme series i7s though, then I agree with fewer reservations. They really are only for those who can afford it because they want to. They aren't needed, and the eight core (16 with hyperthreading) version will actually run games measurably slower, all else equal, due to lower clockspeed.