I guess you not opened your eyes, because they already sold at same vendor, in a smaller quantity. like 1k when an instance comes up. So when a pickzone comes up, the vendor is fillled up.
Also something to note. Etching tools, Small bottle of soy sauce and vegetables, will cost you nothing. That is right FREE, FREE, FREE as many as you want. I assume this is a bug.
It's not the only recipe calling for ancient materials. Belts require like 6 different drops from sof, poi, or dodh.