To save you the trouble of having to dig through every single guide each time you're ready to spend your funds, we've compiled a handy dandy guide that lists (almost) every cost, the exception being Ability tier upgrades.

APTITUDES

Primary: 15 + 5 per additional investment
Secondary: 20 + 7 per additional investment

1st: 25 + 10 per additional investment
2nd: 31 + 12 per additional investment
3rd: 39 + 15 per additional investment
4th: 49 + 19 per additional investment
5th: 61 + 24 per additional investment
6th: 76 + 30 per additional investment
7th: 95 + 38 per additional investment

Bonus tier: Cost of the last tier investment + 5 per number of times invested

If you don't have a Primary and Secondary selected, the first aptitude cost starts at the 25 per tier mark, and the 8th and 9th would cost 119 + 48 per investment and 149 + 60 per investment, respectively.

ATTRIBUTES
1st tier: 15 Funds
2nd tier: 20 Funds
3rd tier: 25 Funds
4th tier: 30 Funds
5th tier: 35 Funds
6th tier: 40 Funds
Bonus tier: 25 Funds + 5 per number of times invested

E-Rank: 2 Funds
D-Rank: 4 Funds
C-Rank: 8 Funds
B-Rank: 12 Funds
A-Rank: 16 Funds
S-Rank: 25 Funds

E-Rank: 2 Funds
D-Rank: 6 Funds
C-Rank: 10 Funds
B-Rank: 16 Funds
A-Rank: 22 Funds
S-Rank: 30 Funds

E-Rank: 0 Funds
D-Rank: 3 Funds
C-Rank: 8 Funds
B-Rank: 14 Funds
A-Rank: 25 Funds
S-Rank: 40 Funds

Minimal: 15 Funds
Simple: 30 Funds
Average: 45 Funds
Difficult: 70 Funds
Extensive: 90 Funds

D-Rank: 20 Funds
C-Rank:  35 Funds
B-Rank:  55 Funds
A-Rank: 80 Funds
S-Rank: 110 Funds