thats really just people being foolish.
or wanting to clear quests fast/easy.
if u can wait, the prices will fall eventually.
the only thing worth picking up right now is the twitherym scale and umbril ooze to get watercrafting, which gives access to the rest of Foret - the lack of which might put you at a disadvantage for harvesting in Foret, and access to Tchakka, which isn't even a concern at the moment.