I count 110 Block Erupters. The absolute cheapest price I've ever seen them is 0.24BTC, which is 26BTC, and that doesn't even cover the cost of those crazy expensive USB hubs, which I would guess add on another 3-4BTC.

I'm sorry, but you can buy a used 60GH/s Single for that price, and it will use prolly right around the same power consumption.