this guys advertises all the time on craigslist here in the bay area. and he is only like 10 minutes south of where i live. from what i hear...he is iffy on pricing. he posts various prices on craigslist that are diff from the pricing on his website. i heard he takes the lowest price you saw it for.
i saw an ad for a custom fixed gear built for like 500. bikes look good...never seen them in person though.