Nobody's going to make a living out of that profession if a monster like that gets you 200 yen, the price of a WcDonald hamburger. Even if they were scammed, it changes nothing. If they scam people who bring in better stuff, they probably do it with lesser stuff as well, and nobody can live with such earnings. I somehow doubt the spirit warriors can go ebay the stones either, so they are stuck with the scammers. The so far unknown organization really found a way to destroy spirit warriors by making the trade economically impossible. I suppose the only way for the spirit warriors to recover would be to stop selling the stones (to their enemies) and instead charge affected outsiders for the exorcism.

Well, assuming anybody does it for living. But if they don't, then why would they do it in addition of their real, ordinary jobs and then bother to sell the stones?

A damn fine episode in any case, for reasons Ryll already mentioned.