If you could convince someone to sell you a box full of Block Erupters at about $1 each, then they'd be great. At about $5/each, they'd be so-so (and still about to be obsoleted, cost-wise). Anything more than that, and they're just not worth the cost anymore.
Even for $10/each, you can take all of them, and then sell them on eBay for profits.
