The 3rd Age Pickaxe is the most valuable item in Old School RuneScape.
If it is converted to RS3 gold the pickaxe is the most valuable item in the whole of RuneScape.
The pickaxe is currently worth:
11.8B (OSRS GP)
Price History
Obtaining The Third Age Pickaxe
To buy a 3rd Age Pickaxe, the best place to go is World 302 at the southern end of the Grand Exchange. This is where 3rd Age items are commonly sold and bought.
To get a 3rd Age Pickaxe you can obtain one from a Master Clue Scroll. The droprate is 1 in 313,168 per roll.