Intel throughout their entire line up generally has 100mhz increase = $10 increase in price
I did not even consider the 3570 at the time of my build. It was the 3470 or the 3570k. Went with the K cuz i wanted to OC and my games were single threade limted so need more omph OC could give me.
If your games are generally well threaded you can get the 3470 on a h77 platform.
If the games are not so well thraded, you can get the 3470 on a z77 board and boost the turbo to 3.9/4ghz os get the most out of the chip.
Where I live, a decent z77 board cost about the same as h77 and the B75 is only $10 cheaper but with too many feature cut out.