[Lastseer]

Look the bottom line is wasted construction.

If a miner II takes 2 turns to build (who cares why, maybe a race has lower production) and a minter II takes 3 turns. It may make sense to build the M-2 and upgrade to M-3 later because the upgrades can be grouped and you'll get to all M-3s faster (less wasted construction). However it depends on why they each take that many turns. If the M-2 takes 2 turns because it's really 1.1 and the M-3 takes 3 turns because it 2.95. Then the M-3s may be a better build.

All this ignores intermediate output and only considers fastest time to maximum output. It works better with ship design. If you have a ship design that takes 1.02 and thus 2 turns to build. Redesign an intermediate design (which differs by less 3 components) which can be build in 1 turn and then retrofit. Your first ship still takes 2 turns to full operation status, but you get 1 ship a turn after that instead of every other turn.