I don't think anyone has mentioned this, but it appears AM is no longer making gen1 USB block eruptors (and maybe blades but the phrasing isn't clear and I was expecting 500GH at some point). According to BTC Guild production of gen 1 has stopped:


Block Erupter Price Cuts / Blades Sold Out
USB Block Erupters have recently experienced another price cut, now at 0.12 BTC (free shipping within US). ASICMINER is stopping the production of new units, so remaining inventory is limited. ASICMINER Blades have now completely sold out as well.

October 10th, 2013

https://www.btcguild.com/index.php?page=home



Edit: Could gen2 be sooner than we think?