Performance per price goes up relative to older hardware, but that's not the case relative to the current games. For example 2.5 years ago a 9800p would cost somewhere around $400-$500, and it could run all the games of that generation at 16x12 without problems. Now you can get a much more powerful x1800xt or 7800gtx for the same money, but it wont even run demanding games like FEAR or COD2 at 1600x1200 smoothly.
Also, I feel the jump in performance this gen was not as big as last gen. A x800xt pe or a 6800u was somewhere 2x-3x as fast as tha 9800xt from the previous gen. This time around, a 7800gtx is nowhere near 2x as fast as the x850xt pe in most games, and yet the msrp prices keep going up. The x800xt pe came out at $500 msrp, and about a year later the 7800gtx launched at $600 msrp. So even though the cards keep getting better, the prices increase even faster and the games are becoming ridiculously demanding on the HW.