The only benefit to doing an upgrade right now as I see it, is ensuring that your starbase has the components you want in case you need to build one. It isn't that you can't afford the reactions, but if you pass up on it now, we might all pass before you're able to construct sufficient defenses.
Tapper passed, morgoth will likely pass, twelve will likely pass and I will also likely pass. If all that comes to pass then the final pass passes us on to the combat phase regardless of who went last during the action phase.
Passably Clear?
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Upgrading now instead of passing, you'd waste money and might not get the chance to build a starbase at all if the other players pass first.