Is this actually a problem on here? Or is everyone getting into a big punch-up over a hypothetical situation?
Personally, since i joined the forum in 2009/10 I haven't seen anyone try to properly 'flip' items the way a power-trader would. Sure, a few people might ask for 40 or 50 quid more than he paid for something, but as has been said so many times before, an item is only worth what someone is willing to buy it for.
I always sell stuff for the same as what I bought it for (or less), but I don't feel the need to get outraged by how much another member wants for their bass/cab/whatever. If any serious attempts at flipping do happen, then they will get dealt with in the ways the mods have already pointed out.
I think by far the more serious problem at the moment is the sheer amount of arguing and personal insults that people are throwing at each other recently. Come on guys, none of us are that bad really, are we?