Let's say that I have a 92FS I wanna sell for $550 but I haven't been getting any bites on it I may then be open to trade it. But, I don't REALLY want to trade so I will require that if someone wants to trade their item must be worth $650.
That way I get rid of a gun I don't want and maybe get something better. Then the guy who has the higher end gun wants to get rid of his and really wants a 92 but doesn't have the cash to go and buy it.
That may be a scenario... It is kinda silly, but it happens (shrug)..
I don't think it's shady. It's just his way of saying he doesn't really want to trade, but if that's all you got he wants to end up on top of the trade.