What is the highest paying loot in Sea of Thieves?

I'm curious, what exactly is the most lucrative loot one can find in the vast and treacherous world of Sea of Thieves? Is it a specific type of treasure chest, a rare artifact, or perhaps a unique commodity that commands a high price on the black market? As a seasoned pirate, I'm always on the lookout for the best opportunities to fill my coffers, so I'm eager to learn about the most valuable prizes that await those brave enough to sail the treacherous seas in search of adventure and riches.