This question has been asked before and no one knows the answer, perhaps now someone do.

I'm looking for a module which the public can join a group buy(public) and get discount. For example

Product A buy Alone is $XXX dollars
Product A buy in bulk of (minimum 5) is $XX dollars

The bulk purchases need not be by the buyer, it can be anyone who join the group.

Is there a module like that, if so where can i find or its plain impossible? Appreciate if someone could just give me a straight answer.