I'm a craigslist junkie, almost never buy anything new. When I started looking for a bike to get back into BMX, there were plenty of options in the $100 range. Many weren't chromoly, but like anything on CL, be patient and eventually it will turn up. Also, if your budget is limited, I saw a few people that were willing to trade their bike for something else. I posted a singlespeed for sale, but was willing to trade for a BMX and actually got several emails for it.