I don't see a problem with price coming down. It's basic market principles of economics at work.
As supply of a good or service increases, assuming the good or service is of uniform quality, consumers are less inclined to pay higher prices because there are other sources for what they want. Thus the price decreases to the point at which the consumer values the good or service. And the market reaches equilibrium.
When DMS was only opened to people with amulets and gems, the supply was more restricted. So the consumer was more willing to pay a higher price. And so with that restricted supply the higher price was where the market equilibrium was.
People who desire the price to reinflate should seek to limit the supply if they really want, but with people constantly doing DMS, supply is ever increasing.