One factor that informs most of our present cost for upgrades or major maintenance is Inflation.
I was told when we bought our boat that it originally sold for about $90K, in 1988, and that did include a number of factory upgrades.
That amount today would be $239K, per the "US Inflation Calculator".
The current cost to replace a lot of parts and systems will not be parallel to that, but it is likely somewhat close.
We can choose to re-equip from a selection of similar parts, over a range of pricing. So at least we are not locked into spending any given (high...) price.