Agree with others ... it will depend on the dealer and what specials he might be running at the time. Sometimes my dealer will run a "$500 off this machine when you trade in any machine" or similar. My dealer will usually run these specials for the high-end machines only. Which brings up the other thing ... many times the dealer will base the price he is willing to give you for your machine, against the price of the new machine you are willing to purchase. The more $$ you spend, the more $$ you will get for your machine.
When considering if the dealer price is not equal to what you think you can get on E-Bay or Craigs - factor in the cost of E-Bay, boxing, and scariness of Craigslist with strangers coming to your house - SOOO much more convenient to drop the machine off at the dealer and be done with it.