How do you know what the average selling price is? The only way to obtain that kind of information would be to have a large data set of recent sales of the exact item in your area. Kind of like comparables for real estate.
With Craigslist, it is my experience that people want cheap. If you offered a pen for sale for $1 you would get 10 replies with people asking if you'll take 50 cents or 75 cents. I have an ad now for 5 JBL speakers and I priced the whole set at $225 and no responses yet although I'm surprised I haven't gotten any responses asking if I'll take $100 for them.
One way is to go to a stereo shop that takes trade-ins or a pawn shop. They have a book called the Orion Blue Book and it's exactly what it seems- a blue book for audio equipment. This is compiled by taking minimum and maximum trade-in allowances with respect to condition and selling prices, WRT to the same. Another way is to look on ebay in the completed listings. google is your friend and all of these will get the info someone would need. Looking on Craig's List is a decent way, too. If you do a search for that model in different parts of the country, you'll see a pretty good cross-section of conditions and prices.
Timing is another think that makes a difference. Nobody will make a killing right now, with so many people out of work but some models will get what they normally get, because of demand. Location is just as important. As far as being cheap, why did you post them in Craig's List? Oh, yeah- it's a free listing.
I don't know where you are but I know of a guy who buys and sells every pair of Polk speakers he comes across. That's one of his favorite brands.
