They retail from AA in the US for $18 each, but are available from limited wholesalers for $6 in quantity with free shipping, presuming you convince them that you're a screenprinter and won't be selling them unmodified.
200 of them is only $1200 that way, and it'll last me 3-4 years easily.
[1] http://store.americanapparel.co.uk/2001.html