Sorry to bring this to an abrupt end, but it looks like there is no such singularity, although it does get quite good, and I've been kind of sucked away from this AAR.
Here's a screen:
As you can see, the tooltip says 99% reduction, but the actual reduction from Practical is only 60% (there is also the bonus from Industrial Efficiency). Still, that's a 6.25x efficiency multiplier in terms of IC-days, not bad at all.
The idea was to match the construction time to the time it takes to research Advanced Construction Engineering. Infrastructure runs up your practical far more quickly than anything else--about 40% the IC-days of bases per practical. I don't know whether the extra IC from factories would be enough to offset the delay in starting building infrastructure.
Here's a screen:
As you can see, the tooltip says 99% reduction, but the actual reduction from Practical is only 60% (there is also the bonus from Industrial Efficiency). Still, that's a 6.25x efficiency multiplier in terms of IC-days, not bad at all.
Umm why are you building those bases and infra? To get +1 practical from building factories you need 1732.4 IC/days - just a smidge more than airbases (1706 IC/days) and navalbases (1708 IC/days). But if you build factories you get their IC and the practical.
The idea was to match the construction time to the time it takes to research Advanced Construction Engineering. Infrastructure runs up your practical far more quickly than anything else--about 40% the IC-days of bases per practical. I don't know whether the extra IC from factories would be enough to offset the delay in starting building infrastructure.