That's not exactly scamming imo, theres no social engineering/trickery involved and relies on really stupid people to buy your stuff. Barely anyone will buy them unless your a credible person and well known/respected on your server. You may aswell put a CL1 weapon on the vendor for 5mil, the people who buy your backpack will be the people who will buy this weapon. A good scam is where you can trick anybody and get away with it.
In a game like this it requires a "long con" to scam people. You will have to befriend certain people and gain there trust to make it worthwhile.