You are concerned with oversaturation of mythic and arcane items. Eventually the mythics will go the way of Lunar Pendants and Fangs of Fenrir.

Lots of MMOs have a complex crafting system that incorporates a "salvage" option. Basically, you can destroy any item of any rarity for crafting ingredients. Mythic item gives mythic crafting ingredients. Arcane gives arcane ingredients. Those ingredients would be used in crafting more legendaries, mythics, and arcanes basically.

The idea is creates both a demand for mythics/arcanes and is a supply regulator essentially. Prices would not drop to 20k per mythics or anything of that sort. AL's crafting system is still primitive, so it would take a while before the devs decide whether or not to implement it. I personally think that it would be helpful in the long run.