The calculator seems to be assuming capex costs don't increase over time with traditional data centers but that they do with orbital data centers, due to hardware failure. That does make some sense in theory; terrestrial data centers don't get completely destroyed on re-entry, though I think in practice there are other costs associated with aging terrestrial infrastructure that are being omitted here.

I guess we'll see. I think though that given we're now arguing over the particular assumptions used to estimate manufacturing cost rather than over physical limitations I've sufficiently made my point.