Harmony - Troop Symmetry

Decided to compare the effectiveness of the "Mana Attraction" and "Secret Knowledge" skills:
We will compare them based on how many times the same spell can be used.
So, we have:
x - total mana volume;
n - cost of a spell;
z - coefficient of increasing the total mana volume from "Mana Attraction";
y - coefficient of reducing the spell cost from "Secret Knowledge".
We get the following formulas:
1) x/(n*y) - number of spell uses for a hero with "Secret Knowledge";
2) (x*z)/n - number of spell uses for a hero with "Mana Attraction".
For these perks to be equivalent, the results obtained must be equal - that is, we compare both formulas and, after simplifying the expression by reducing x/n, we get:
1/y = z
Therefore, with a 20% discount (the spell cost becomes 80%, i.e., y=0.8), we get 1/0.8 = 1.25, i.e., the increase in mana volume from "Mana Attraction" should be 25%, not 50% as in the original.