Yeah I see your point. I've never really known any other site to sell on aside from ODT. Don't you need to be FFL to use Gunbroker? And I've always heard bad things about armslist. If I'm wrong PM me!
No need to be an FFL on gunbroker... Typically need to ship to a FFL for the buyer and then the local FFL would do the standard tansfer forms. Gunbroker is the really the place for true high-end, rare or collector type guns. Much larger audience with some dudes with deep pockets and willing to spend it get what they want.
Don't get offended by the low offers. Many are just offering what they are willing to pay for it. One man's treasure is another man's trash and that goes both ways.