How is This Possible?

[kaisim_2492829]

really then tell us how
the approximate costs are

11-12 250m coins
10-11 125m
9-10 75m
8-9 38m
7-8 19m
6-7 9m
5-6 5m
4-5 2.5m
3-4 1.25m
2-3 750k
1-2 375k

so a level 12 rune is about 525m coins start to finish

How can you do it for 300m without synergy

to make a level 9 rune in temple is about 60-65m, upgrading that 9 to 10 is the same amount.
your list is wrong either way. 10-11 is stated 125 which is 2x10 according to your own list 150m and not 125m, why would they get more expensive?