At the current price, not at all. Unfortunately the frenzy for the Eruptors has caused their price to be ridiculous. So the return just isn't there. On the other hand, if you can get your hands on one of Avalon's units or a fabled BFL unit the return is there. The Eruptors really only make sense if you are buying in large quantity. If it costs you more than $250 each there's no way you'll ever get the money back unless BTC makes a huge jump in the currency market. They really looked like they were going to become the mining unit of those without the funds for larger rigs, but so far the prices are too high to make it happen.