3 out of the 4 AEGs I've purchased were used. No problems except the rear receiver tabs broke on the M4, but that's normal. My thoughts on why people charge and pay 90% of new value for used guns is because people want to try as many AEGs as they can before settling on the one they like best. So someone buys a new AEG for 500$, decides it's not for them after using it once and sells it for 450$. Second guy sees the gun he wants that's practically new for a saving of 50$. He realizes he may do the same thing as guy 1 and sell it soon after getting it. It's unlikely it will break in this short of time, and he can list it as "good as new" and probably sell it for 450$ again. He basically gets to try out a gun for free, whereas if he bought it new he would lose 50$. So it seems like a good idea to buy used rather than new. Of course it continues getting traded around and listed as good as new, and the price doesn't drop much. Everyone's happy until the guy who has it when it breaks.
Basically, if I was 100% sure I was going to keep the gun I'd definately buy new, if not then slightly used seems like the way to go, and seeing that I've sold 3 out of 4 AEGs I've owned, I've saved a lot of money by buying used, even made a profit off one gun.
The Doctor is in.