Nope, GTX660 is 25-30% faster on average. Main reason is just old stock - retailers buy huge stocks of hardware and sometimes the old stuff they forget to reduce as time goes by and newer stuff comes out. Plus, it obviously makes it look like a more attractive deal to people if it's normally ultra expensive! That 560 Ti is only even a 1GB card anyway - not great for future-proofing. GTX660 is a solid bet.
though if you toss in the rebate making the 560ti $149.99 that is a good deal for that card. it does lose to the 660 by ~20% or a little more depending on the game. it would be better to compare it to a 7850 1 gb making it a really good deal being $20+ cheaper; it overclocks like a champ and will leave any 7850 in the dust.
edit: sorry i didn't answrer what you were really asking though it was touched on; the $300 was the price at the release, the seller, new egg, listed it to let buyers think there were getting a stupendous bargain, when actually the $150 price is what the worth is now.