In the original release of D2:ED, the Mindread skill was generally considered to be not worth boosting (a minority did). Presumably the higher costs are partly to make the skill more important.
The experience needed to level goes up in proportion to the cube of the level, so the costs to mindread also have to go up, to maintain the relative cost/reward benefit for stat and skill points, at least.
Opponents respawn in some areas in FoV, and I assume give more experience than the regular opponents at the end of D2:ED (haven't got that far yet). The debt shouldn't last significantly longer than in the earlier portion of the game, despite the higher values.
There are many skill points available from quests and mindreading in FoV, so you can easily max the Mindread skill.
