How does it make any sense of what? Potions are alchemy and shark oil actually IS alchemy. Rest of the ingredients are not as they're all from gathering jobs. Them being "rare" (expensive) ingredients for you doesn't mean SE should make adjustments to it.

Fisher retainer can fetch you 3 sharks per 1 hour, which you can select either hammerheads (lv29) or silver sharks (lv 41).