It's even more unkind on pure runs (especially nightmare) that wants to, and effectively needs to, buy them up front on day 1 at minimum price.
Day 75 is a LONG time. Yes, they might be cheaper after day 75, compared to before, but they still need to be bought in those first 75 days at their cheapest to be efficient. That is a LOT of money. The PRICES might break even at day 75, but you would have ALREADY spent much, much more than that prior I would have to imagine.
It feels to me as if the only maths done was that if you buy all the holy waters on 75 they're equal to before, and cheaper after.
But if you bought them at their earliest availability at each increment, they're much more expensive before, and will take longer than those 75 days to become functionally cheaper.
On nightmare for example, you're buying 5 x 504 for 2520 gold on day 1, this is absurdity.
The day 20/21 restock of 2 will cost 2 x 580/584 for 1060-68.
The day 40/41 restock of 3 (post greed) will cost 3 x 660/664 for 1980/1992.
All up these 40 days of waters costs just over 5.5K.
Previously.
Day 1 - 5 x 208 = 1040
Day 20/21 - 2 x 368 = 736
Day 40/41 - 3 x 528 = 1584
Totalling about 3400 hundred.
There is a magnitude of difference in the dent it is putting in the EARLY wallet. They might be cheaper at the equivalent time later, and eventually reach a point of overall superiority, but it is STILL cost effective to buy them at these points.
It feels like you're saying we shouldn't buy them until we need them, but that's ludicrous and cost-ineffective. The early wallet can't take this, but the later wallet COULD take what happened before, the increases probably just needed a cap somewhere as the game expanded.
IMO - the solution should be a reversion to the original base price with the reduced per-day increase, but with each restock itself having a separate unique increase.
The consequence on the early wallet is too great with the later pay offs not being worth it IMO, money management early is a far greater issue. 1500 early is worth WAY more than 1500, eighty days in.
Again, I also see that you're tackling this from a corruption playthrough view in regards to willpower maluses, but pure playthroughs need them incredibly regularly as a result of needing to avoid forced-masturbation and lack of other corruption removers.
The early cost is too great on beginning a playthrough.
I don't find day 100 a good benchmark because an effective playthrough needs to be beating those generals before then, so parity happening so close to that milestone is a problem that impedes progress. Think of it in the same way as using the church to bless bombs early. It costs money, and not using them is cost effective, but there are faster returns if blessed bombs allow you to make progress somewhere sooner. It's similar logic here. Losing this money to early holy water purchases impedes your expenditures elsewhere to make progress. If you don't buy them up front, you're spending more later.