However, we stand by our decision not to have the highest-level gear available for purchase. One of our primary reasons is that such a change would encourage RMT. Our team is working tirelessly to stamp out RMT entirely, closing thousands of accounts and seizing massive amounts of gil every week—this even in the game’s current state, where many believe that crafted items are in low demand.
Solution: Make the gear untradable-on-craft. Thus only players who happen to craft the item itself can keep it. Similar to Rare/EX items in FF11 obtainable from NMs that was to fix sellable random NMs by RMT.

While the materials would be tradable, its result would not.

Another solution would be crafter dungeons to obtain the mats. Whichever way is chosen, the end result should be bound to the crafter when crafted, such that it cannot be traded (it can just be made Untradable instead of Bound - like many items are).