Couple of thoughts (and a free bump):
1) The economy *****. Consumers aren't making discretionary purchases, and an air compressor for most hobbyists is a discretionary purchase. Unfortunately, it doesn't look like the economy is going to improve anytime soon.
2) The weather *****. Indiana, like a good part of the country, has been in the deep freeze for nearly two weeks. Lots of folks on this board have big, climate controlled garages, but those folks aren't looking for a lower-performance air compressor like this. People looking for a compressor like this have an uninsulated garage with an electric space heater. They're looking to upgrade from their CH 2 hp pancake compressor, but with the weather we've been having, they're inside watching the playoffs and not thinking about air compressors. Warmer weather should bring out more buyers.
3) Because of the size and weight of a compressor, your potential market is local, or at best regional. Someone has to drive to Indy and pick it up. So selling a used compressor is going to be infinitely more difficult than, say, a set of wrenches which you can box up and ship anywhere.
If you want to sell the compressor as quickly as possible, change the price to $500 or best offer. You might get some lowball offers (you can always say no), but at least that will give you a better idea of what the market actually is for your compressor.