Many threads on this already so search search search...

Briefly, if you are looking for a complete bike for under $400, search ebay for a Mercier Kilo TT or Windsor "The Hour" bike - rebadged KHS and Fuji bikes, respectively. Both go for about $350 complete with not so hot components on decent frames.

Used Bianchi Pistas seem to sell in your price range on eBay fairly regularly.

m.