The

Character sheet page of the wiki gives an explanation. ToME's diminishing returns are probably great for balance, but they can make scaling really hard to figure out. 1.3 has a small usability boost in that equipment will tell you both the raw boost value, and the effective boost from equipment.

Here's the relevant text:

**Quote:**

It costs more to increase scores that are in higher tiers. For each tier, here's the cost of increasing your score by one:

- Tier 1: 1 point, from 0 to 20
- Tier 2: 2 points, from 20 to 40
- Tier 3: 3 points, from 40 to 60
- Tier 4: 4 points, from 60 to 80
- Tier 5: 5 points, from 80 to 100

So, assuming you don't have any equipment that boosts spellpower, 45 spellpower + (0.21)*25 cunning = ~50 base.

0-20 points -> 20

20-40 points -> 20+10 = 30

40-50 points -> 30 + 10/3 = ...33, apparently.