Where are you seeing prices like that?
The cheapest I've seen is 220$ for the i5 750, and 300$ for the i7 920, compared to 190$ for a Phenom II 955.
And of course, with AMD, you also get cheaper motherboards, backwards compatibility (an older AM2 or AM2+ will take the new AM3 CPUs), cheaper memory (can use DDR2, and you don't need triple-channel kits), and what have you.