When people win a claim, they win the right to anything the monster drops, whether it's the right to keep the items or sell them is up to them. If they lose that claim, you have the chance to claim that right from them.

Likewise, if you don't like that X player is spamming Charybdis just to sell the sword or something similar, just outclaim them. You have as good a chance as they do, assuming equal levels of speed, skill, and attention.

SE has always allowed players to do pretty much whatever they want in terms of finances. No one is getting scammed. People are just purchasing the right to lot on an item.