I kinda feel the problem is that the devs know they can't limit players to only a selection of the weapons due to their philosophy that you can play all jobs on one character. But somehow (perhaps by requested from Level 5?) they don't want to let players have everything. So in the end it became RNG plus FATE farming with price escalation.

Frankly this design seems completely opposite to the philosophy of accessibility that has been present in the vast majority of FFXIV content.

I can just move on if it's limited to cross-over events like this. But I seriously hope this doesn't get applied in actual FFXIV content. Imagine each time you buy a piece of Creation gear, the next gear of the same slot is 10% more expensive...