Its due to bad promotions people stopped buying loot boxes and item generation in game slowed down which is the reason why prices went up , more people buy boxes more will get crappy reward which they dont need "Greater Runes" in our example, and they will sell these for fraction of the price as there would be loads of these,
In game item generation does not exists so its down to pay boxes to help people get items.
No boxes opened = no items in game,
Pretty simple.