I'm being won over by the difference between natural and synthetic crystals being fluff argument. I think I'd probably say that the the players have to pay the cost of an Ilum crystal for the materials required, but at the end of the process they have a working synthetic crystal. I would say that at least one part (maybe the furnace or the stuff that will actually become a crystal) falls under Restricted and requires a quest to get or something.
Yep. And don't forget that you're going to need about 700 Credits worth of crystal polish to get a nice, smooth mirror finish that's going to get the most out of that crystal, which the Devs, in their infinite wisdom, just made all that much easier to do...