Dropping production costs for post-Industrial units may be a bandaid, but it could also be just enough to smooth out this wrinkle. I agree that inflating tech costs is the worse option as it does nothing but drag on the game for non-Domination victories. I've commented before that the
cost versus
cost of post-Industrial units needs adjustment as it is currently way too inefficient to produce new units in the later Eras given how many relative turns they require. Even in cities with full to near-full
infrastructure (Ex: All
buildings save for maybe a coal/nuclear/solar/wind/hydro plant) it takes 10-16 turns in Epic (6-9 turns Standard) to produce Bombers, Tanks, Machine Guns, etc. In that same number of turns I could build two new buildings or a Wonder, or if at war conquer several cities. And that's for a high-production, non-Capital city with full military infrastructure. Once you get to the Modern Era things progress at a rapid pace if you're playing well, unlocking new technologies every 10 turns or so (again, on Epic) with lots of Great People and instant yield bonuses to speed up Tech and Policy accumulation. Wars start and end over the course of a dozen or two turns, and entering the Modern Era means you suddenly have to start worrying about a large variety of unit types. You can't just upgrade all your old units as you'll need to start producing submarines, AA guns, aircraft, missiles, nukes, and carriers all from scratch. And with the unit
costs currently as they are, there just isn't enough time to make all these new unit types before you move on in tech. Thus I almost always end up
purchasing new units rather than producing them.
I'm not suggesting anything major here. I think a fare start would be lowering
costs for Modern Era units by 10-15%, and then Atomic and Information Era units by 15-20%. Then increasing the
purchase costs of these units by at least 10-15% as well.