I'm going to buy them and exchange the BTC for Litecoins, which currently cost waaaay more power to generate in comparison. So I really don't feel bad. I will keep them running until they can no longer profit.
You would do better to buy some bitcoins and use those to exchange for litecoins.
Or, you know, buy some litecoins.
If you buy a block erupter at this price, you are guaranteed to get less bitcoin than if you just buy bitcoins. You will also get those less bitcoins over a longer period of time than just buying some bitcoins. So if you want bitcoins, buy some bitcoins, don't but a block erupter.
Same logic applies to litecoins.