Tanning cowhide

⚠ This profit comes from buying, processing, and reselling on the Grand Exchange. It assumes large GE volume and can be inflated or volatile — treat it as a theoretical ceiling.

Hard leather is used to train Crafting in free-to-play, and it is in reasonable demand. Because it must be tanned before it can be crafted, tanning cowhide into hard leather can be quite profitable at times.