I plan on running some and selling some on Ebay. Profits from Ebay means I won't need to cover the cost of the ones that I do run.
Assuming the price of bitcoin will remain the same... - if, in a years time from now 1 BTC = $500 dollars then these little usb gizmos will have been a steel...
doesn't work that way. you could just buy 2.2BTC instead and have no energy costs and make 1100.
at this rate, a USB miner won't ROI, ever.
But where is the fun in that?
Looked at from a purely financial aspect, these are not a good purchase unless the USD price per unit stays the same but the BTC --> USD value increases or the BTC price of the unit drops.