With the availability of teleportation technology within the City, it's possible that raw materials are brought in from outside the solar system, though the sheer distance would be prohibitive I think. There seems to be limits on teleportation range.

Also it's implied within Blame! and so on, that the Level 9's ultimate attack is opening a portal to the sun.

"I really think that this weapon was transmitted from another world.
Assuming that that's true, I wonder if it came from the surface of the sun."

Who knows!