Even when the requestor is the defendant? That seems open to abuse: The government sues someone, and then they have to pay huge sums just to get the documents to defend themselves.
I'm not a lawyer, but there are many ways the legal system can be weaponized.
My understanding is all evidence that can be used during trial must be turned over to the other party (barring some Perry Mason type last minute discovery that occurs during trial).
If as a defendant, you request documents, and the cost to reproduce is so "huge" as to be a burden towards justice, I imagine you could take that to a judge with a motion to compel, and have the cost amount knocked down substantially.