It could be said that because they have to physically go and find the document, and hand it over for you to take a photo of is the reason for the costs.
That would make sense, but in this particular case the fee is for copies of deeds and other public documents that are in bound volumes in the record room.
There still is the cost of making and maintaining those volumes, for building and maintaining the record room, for having somebody check how many photos you made, for billing, etc, etc.
With fairly high fixed costs and, likely, demand varying a lot as a function of price, picking a break-even price point isn’t really possible up-front.
For example, if they were to charge $1,000,000.— per page, chances are they won’t recover costs, but that doesn’t imply they should ask more.
I think governments should just give up on the idea of recovering costs on this kind of service. That may mean some people will benefit more from it than others, but then, be that so. Alternatively, put a reasonably high cap on the ability to query the system.
It’s entirely self service.