Ruby

Ruby is a free-to-play item on the OSRS Grand Exchange in the other category.

In-game examine text: "This looks valuable."

It has a Grand Exchange buy limit of 13,000 every four hours, a high alchemy value of 600 gp, and item ID 1603.

View on OSRS Wiki

Ruby shows an active flip setup with a margin of +4 gp and 1,813,233 trades over the last 24 hours.

At the buy limit of 13,000 every four hours, max profit per cycle is about 52.0k gp — high margin with healthy liquidity.