One point i feel i have to make about this.
Markers are shooting far more than, lets say 3 years ago. An average year old marker has done 50 - 100k shots, and is well worn by then, and to expect a second hand price of 20% down on retail is ridiculous.
Most gun designs are sacrificing quality for cost, less weight against strength, and just don't stand up to the rigours of modern paintball.
Be honest, would you buy a marker that's had the crap shot out of it for a nearly new price. When i see a one year old marker up for sale, the first thing i look for is the level of the team the seller has played in.
New models each year has had a bad effect on second hand sales, but if we didn't get a new shiney toy each year, we would be the first to moan, eh guys.!!
Catch 22.