Changed a few spells mana cost, used a modfile. Game correctly reads attributes of new spells (no double damage etc) but incorrectly charges both the old and new price. Double checked, have only one cost entry in spell. 

Example: Arcane Arrow

Original cost is 8

Changed cost is 10

Cast menu in game lists both 8 and 6 and charges both

Second issue is casters ignore int requirement, whether or not it has been changed. Arcane arrow lists minimum int as 20, sovereign was able to cast at 18 int.