No, and here's why:
>it's essentially a shop between players and not player-game
>prices lower between players because no one would buy weapon X for over its store price, causing people to sell it for cheaper than the store prices
>soon item prices will deflate well under the in-game store prices because of this
>less reliance on gralat packs
>less income for developers = bad for a game in the long run
If it's for items that are already droppable/tradable, then whatever. If it's for guns, then no. Even then it's already redundant because of our trade system.