Jeo: Napkin math.
Typical 'decent' galaxy right now seems like around 300 nukes, 1500 metals.
With T16 fusion extractors, the upgraded factories, and maxed ExE, covering every slot (usually unrealistic because you get marginal planets a lot that aren't worth it) that is:
97,000 fusion cells a day
486,000 steel girders a day
Take off 14,400 for the galaxy ownership, and you are at 82,600 fusions a day.
IC gear builds require 25 fusion cells per 40 steel girders, so I'm at a deficit of about 220,000 fusion cells a day to actually continue those builds.
Or to put another way, assuming we're not just 100% set up from the get go:
With T9 extractors and regular factories, that's (after ownership control) netting:
24,480 fusion cells / day
194,400 steel girders a day
For covering every nuke slot in a 'decent' galaxy. 1/5 as many available fusion cells to do builds as we have girders, with the ratios you need them in.