Re: [item]Gem of Mystic
Make the recipe cost 1000, and make the Gem of the Mystic have 1 charge of Farsight, and if you want another charge, you have to spend another 1000.
That's the only way I can see this item being "balanced," if item-based, instant-cast, global Dust of Appearance in DOTA can be considered balanced
Edit: if this item has infinite uses with a cooldown, it'd be absurdly OP. It could have a cooldown of 600 and it'd still be OP, because Tinker would break it with Rearm