Expect the price of this to rise again for the time being.
The main supply of this ore was from the puk ISNM, which people used to spam for khroma ore. Now khroma ore price has plummeted owing to updates providing new ways to get it, so less ISNM-ing, and less lumi ore.
Here's hoping luminium ore will be made easy to get in the next abyssea update!
With the Demand of these going up, and the price of Scintillant going up, then you would figure the price of these would rise as they arent exactly that easy to get, especially needing 3 per synth. These SHOULD go up with the new synths. Ingot demand is going up so should price.