The fact is this card is on the reserved list. Never going to be reprinted in a masters set or Urzas Saga 2 set or some nonsense. The market doesn't care how much you think it is worth. THe market doesn't care how unfair it is that you don't have one. The market says it's worth ~290 as of 5/8/18. The market has spoken.
if mox diamond would enter the battlefield, you may discard a land card instead. if you do, put mox diamond onto the battlefield. if you don't, put it into its owner's graveyard.
t: add one mana of any color to your mana pool.
Does anyone think this will ever be a $200+ card? It's pretty old now and considering it's rarity and age I'm surprised it's dropped in recent years.