I think i have the most money lost on firearm deals. bought an AK in jan 2009 for $750 (worth only about $300-400), sold it later with a scope mount, a scope, a bipod, and a picatinny rail with laser mount with 1,200 rounds of ammo for $450. at the same time i bought the AK i also bought a bullet resistant vest for $210 and sold it later at the same time as the AK, but i sold it for $100. My first gun ever was a Winchester 30-30 i bought for $300 and sold the same time as the AK for $150.
HERE'S the kicker... I traded a $500 pistol, another Winchester 30-30, a 20 gauge shotgun, a bunch of ammo, and a bullet resistant kevlar helmet + $500 cash for a gun worth $1800 (fair trade BTW) and i sold it 2 months later because i needed money for my new house, for $975 as i am typing this today (2 months later) that same gun is worth $3500-$4000. i could have more than doubled my money but instead i got a little more than half. this is all in the last 3-4 years... BEAT THAT fellas!