Thank you for the feedback. If you look at the MH/$ column, you'll see that the ASICMiner USB Erupter actually has one of the worst MHash/$ at 4.

At the current network difficulty growth rate of 62% per month if the device, shipping, and electricity costs were $0, the USB miner could be expected to return 0.41 BTC. Now add in additional costs like electricity and setup costs, and you can determine what the maximum you would be willing to pay and still make a profit. All of the settings should be tailorable to your individual costs and what your projections of network difficulty will be.

http://i.imgur.com/67IjngV.png