Goldman's right about the pricing, devaluation isn't just based on something being "used" and in the case of airsoft, a 2001 AEG that was used 4-5 times a year will probably have much less wear than a 2005 AEG that got used all year, every couple of weeks. And they're otherwise usually identical (if they're the same model).
I check the buy & sell sections daily, and the bulk of what I see are really good deals. Some packages are really expensive, but they include a lot of upgrades, accessories, etc, the value of which is lost on most noobs - not to mention some of the finely tuned stuff performs way better than it did stock. So if you wanna make analogies, compare this one with real estate; you buy a fixer upper, and the property does gain value.
Only a handful of ads were [IMO] overpriced. But for everyone of those, there was an incredibly good deal elsewhere so I guess it evens out.
In the end, it's supply and demand. Airsoft isn't a cheap sport, and people on a really tight budget should really think twice before jumping headlong into it. Prices are what they are because people are willing to pay that price. And if you think this is high, you should have seen prices in the late 90s when new items were barely trickling into the country.
What I'd like to hear from the original poster is what kind of price he thinks items should go for. I can justify current prices if I had to, so how do you justify lower prices besides "its used"?