I've had another realisation about asteroid miners. The shipbuilding rate can eventually be improved beyond the factory production rate (in many decades). At that point, building mining ships would be much quicker than building hundreds of automated mines (and you wouldn't need any freighters).
Even before you reach that point, though, is it not correct that since the shipbuilding rate does not scale exponentially with the tonnage of ships (even with vast multi-million ton ships), there will be a point where you can build a ship in a year or two that has a greater mining yield than the same amount of automated mines built in that period?
Someone help me out with the maths here

For example, in my game I'm on construction rate 14bp, shipbuilding rate 750bp. I can build a mining ship to yield 448 tons per year (per mineral) in 1. 26yrs - and I could build two of them at the same time. In 1. 26yrs I could convert 170 automated mines, which would yield 3404 tons. So this point, the mines are way better. But sooner or later, with a bigger ship, would it tip the other way? (a ship ten times larger wouldn't take much longer to build, but would yield ~5000 tons)