Making fuel on the Moon or on Mars is more or less the plan for any sustainable development of the solar system. Unless we get sci-fi grade engines, it’s just unfeasible to send fuel from Earth.

An acquaintance of mine who works in the industry (not at SpaceX) called Raptor a “scifi engine.”

For a lot of purposes, Starship should make it extremely cheap to send propellant from Earth. $10/kg in LEO. Cheaper than any lunar mining proposal I’ve seen.

That said, I hope we do make propellant off-Earth eventually.

Yeah if I remember correctly, I read that the solar panels required to ISRU make enough methane on Mars for a starship return flight would be two football fields worth and it would take them a few years to do it.

Area is just not a huge problem on Mars or in space in general. It’s not really a relevant figure of merit, unlike mass and pre-deployed volume

That's a chicken and egg problem. Making fuel off of Earth is going to require so much mass for infrastructure that it won't be feasible until we have fully reusable vehicles.