The amount of gold alone that is under the ocean floor is estimated at $150 trillion.
At current prices.
But right now, there’s less than 200,000 tons of above-ground gold. At the current price, that works out to a bit under $10 trillion. But it’s highly valued because of its rarity. Would it be profitable to mine gold from the ocean floor (or asteroids for that matter), if doing so would bring vast quantities of the metal to market, making it much less rare?