Mining nodules four kilometers under the Pacific is not cheap — but the bill looks different from a land pit. Think of the project as two giant price tags glued together.

First comes the offshore kit: a robot crawler, a four-kilometre riser pipe, and a converted drill-ship that keeps station even in four-meter swells. Engineers estimate that the full chain costs roughly USD 2.3 billion.

Second is the on-shore refinery, where nodules are crushed, leached and separated into nickel, cobalt, copper and manganese; that adds about USD 1.9 billion.

Put together, the upfront tab hovers near USD 4.2 billion for a mine designed to lift three million tons of nodules each year.

Running costs come next. Fuel for pumps and dynamic-positioning thrusters, crew salaries, spare crawler tracks and chemical reagents push operating expenses to roughly USD 28 per wet ton just to reach the plant gate.

Once you fold in electricity and acid at the refinery, the full operating cost climbs to about USD 50 per ton.

Spread across the metals inside each ton, that equates to an all-in sustaining cost of around USD 6,400 per ton of nickel-equivalent — noticeably lower than many land-based high-pressure-acid-leach (HPAL) laterite mines, which often need nickel prices above USD 10,000 per ton to break even.

Investors like the lower day-to-day spend, but they still worry about the monster upfront check and the unknown price the International Seabed Authority will set for royalties.

A 2% royalty barely dents cash flow; 6% could wipe out half the profit margin. Add carbon pricing or stricter plume rules, and the numbers shift again.

So, while deep-sea mining’s operating bill looks lean, its final economics depend on metal prices, royalty bands and one simple question: can the hardware run month after month without a billion-dollar breakdown?