They could keep the current artifacts system, but make them point-based, and certain artifacts are worth more points than other. Then players could uses these points to exchange EITHER coins or items. The points for a certain item, lets say a dfs, is 500. So when players exchange them for massive amount coins, the inflation will began, and causes dfs to rise in price. So then people could use the points to exchange for dfs, and sell them, keeping the prices balanced.