Just wanted to chime in and say that lots of places now sell pots and flats for the personal greenhouse. You pay a bit more most likely per pot, but you don't have 3x more than you need. Here are a couple to check out and compare prices.
http://www.charleysgreenhouse.com/224-414-Pots.HTm
http://www.circlehgrowers.com/plasti...astic-pots.htm