[JumpCrisscross]

> It's very close to "Starship to the asteroid belt, capture asteroid, return to Earth orbit"

To put this into perspective, an Earth-Mars round trip costs about 15 km/s; Earth-main Belt about 13 km/s.

You'd need to add Δv for returning the mass of the asteroid. But you get your reaction mass for "free."

(To be clear, we are hundreds of billions of dollars of capex and decades away from asteroid mining. But the work to get there is decently in line with the work we would need to establish a logistical chain to Mars and back.)