Does a small computer use tons of materials , no it does not.
Computers, sensors and cameras, wires and servos to act the AM need materials different from only Corundium.
So, 2 or 3 of every other material in the game + 120 Corundium can make an AM, IMHO. But, I think this doesn't assure us to be saved from Corundium scarcity.
With AM we have now, anyway, it seems to me that we mine Corundium just to mine other Corundium.
... limited population ...
Until now, few times I lacked population. Maybe because I prefer to colonize other bodies quite slowly. Therefore, my manned mines usually have enough workers. But it also depends on the planets types that game generates (i.e. few vs. several good planets, with good starting conditions or easily terraformable).