Agreed- overall condition is a major factor when deciding if a price is reasonable and don't forget how expensive shipping is these days! I paid $125 and $175 respectively for shipping the last two bikes I purchased. The first one was ~9 months old and had one significant pea size dent in the downtube. With shipping included, I paid between 1/4 and 1/3 the retail price (the fork itself was worth what I paid for the whole bike). The second bike I purchased (also ~1 year old) was more like 1/2 the price for a new one.

I tend to look for bikes with higher quality components (Shimano XT / SRAM x7 or better).