It seems like CDs are more expensive now than they used to be. I suppose that's a reaction to the digital surge and less buyers of physical media. But even new CDs often cost more now, not just the OOP ones.
Part of that may be the fact that the Christian scene is comparably small. Our rare stuff is R.A.R.E. Thus, it costs a pretty penny to round out the back catalogues of important bands. Even with newer stuff, it's a smaller pressing and most of the labels opt for quality over quantity and do extensive booklets, gold CDs, etc. which means more expensive. I don't think that it's necessarily that costs have gone up though because Vision of God cranks out new material all the time and sells CDs for $8.99 a pop and color vinyl for $19.99. He runs it as a non-profit though so he doesn't charge much more than cost just to keep things running.
I spent about $50 to get Antestor's "Martyrium" and over $80 for "The Defeat of Satan" no. 2 of 999.