A GTX 660 is a low end card. A GTX 950 is 150$ and ~5-10% faster than a GTX 660.

It is an old card that was fairly high-end when it came out. It matches the graphical capabilities of the PS4 today.

It's not low end, it's mid-range. HD at 60fps (often higher) on med-high settings on everything but the very most recent games (without MSAA).

Again, you'll probably need to wait more than 4 years for a high-end card to become "very low end". I'd give it five or six years.

IMO, sub 150 = low end, 150-320 = mid range, 320+ = high end. The 660 GTX is worse than a 150$ graphics card (GTX 950).

Granted, in terms of hardware people are currently using the GTX 660 might still be mid range.

Right. I was basing my comparison on performance rather than price. But in terms of price, you're absolutely correct, the GTX 660 isn't worth much.