I've seen many threads saying things are free, and then inside they tell you to tell them how much silver you have to haggle with. Is there not a rule about this????  Are you allowed just to post a thread with the title 'FREE!!!!' and then be like 'but not really' in the actual thread?

That's very deceptive, and I feel like there should be a rule about it?

You're right, this is very deceptive, I don't know exactly what to do about it, though I suggest that you don't buy their stuff unless it's a really good deal.