Re: What resource?
It's true that everything in space can be found on Earth far more cheaply, but that is to overlook the one main difference between them. Stuff in space is IN SPACE. It would costs $$$ to put stuff in space, why not use stuff that is already there.
NASA wants to go to Mars but it takes lots of propellant to get there, it would be very handy if you could refuel in space rather than dragging it all up from Earth.