This mod makes spell tomes really expensive, it is intended to use with Spell Research, any mod that makes spell tomes rare, and economy mods that make earning money very difficult and makes more things expensive. With that being said though, this mod has no requirements, except for the versions that have modded spells included. 
Recommended Mods
Apocalypse - Magic of Skyrim - Absolutely amazing magic mod, already have a version with apocalypse spells included
Mysticism - A Magic Overhaul - Another amazing magic mod, currently working on a version with this
Arcanum - A New Age of Magic - Once again, a great magic mod, working on a version with this
Forgotten Magic Redone SE - You know what I'm going to say
Spell Research - Awesome mod that allows you to... uh what's the word, oh right, Awesome mod that allows you to google recipes for spells and alchemical stuffs. I always use this and rarely purchase spell tomes anymore because this is just so fun
Rarer Spell Tomes SE - This mod makes spell tomes appear absolutely everywhere, deer have eaten them, so have dragons, so has that bunny that you chased for hours. JK it obviously makes spell tomes rarer at both vendors and loot, it is also customize-able, check out the mod page to see what values to change.
Frostfall - This will make some of the prices make sense especially if you do the hardcore mode, will probably make a version with spells from this mod
A good Economy overhaul, I don't really know of a good one that fits with this because I just use the one that I made. I don't plan on releasing it unless there are significant requests for it because... Well I'm lazy. But really it changes the price on every item in the game that is purchase-able and if I release it then I would have to spend a significant amount of time tweaking it to make more sense and be at least attainable for people who don't want to make the economy of this game give you heart attacks.