Some of us just like to barter. I'm fortunate that I have a good job and enough income to meet my needs. I'm not wealthy but I don't need cash.
I do agree with the OP that posting two prices is a little odd.
As a matter of fact, since I don't sell many guns and do trade a few, I feel that posting any price is counter-productive and will usually decline to do so.
Relative value is not at all difficult to determine between two (even as many as three) individuals: If I want what you have to offer and you want what I have to trade, we're good to go, sometimes with minor adjustments.
I have a personal trade policy in which either party, if unhappy, can return to zero with the unhappy party paying all shipping and fees to return so. I've never felt I was involved on either end of any shadiness.
If you've got something to trade, PM me