The difference depends on the story situation:
- Are you on the market in a big city? Of course you will be able to buy pretty everything as long you have gold.
- Are you in a prison on an isolated island? How the hell are those merchant prisoners and seekers getting all their stuff?
Making everything just more expensive would make economy more dire but in no way make immerssion more believable.
This thread is about the economy of the game, not about immersion.
Besides, it's more believable that the vendor sells books you can't afford than books you can afford. So it does make it more immersive to make stuff more costly.
If you want more immersion, then ask for merchants that make more sense. A lost spirit in a hidden or underground library that sell spell books for all school of magic for example instead of so many merchants all over Fort Joy.
