Reverse logistics will get Elons colony in the end; tech upgrades require regular decommissioning and replacement of tech. Can’t have those precious metals like gold connectors just laying around mars. Gotta send back to earth. Reverse logistical nightmare.

The key is century proof tech – tech proven to reliably run for centuries with little to no maintenance. This will take a long time even the experimental stage probably would set us to 2500 for earliest practical Martian 1+ million population colony feasibility