Fair point. From what I can tell, refined tungsten is actually an order of magnitude cheaper(!) than refined silicon, but molybdenum is over two orders or magnitude more expensive. ~300USD per ton, ~2000USD per ton and ~60000USD per ton respectively.

I assume that if this got up to scale industrially, savings could be made by recycling high purity molybdenum waste, but yes, it's not going to be cheap.