The Actual Cost of Prestige Skins

I was just wondering how much the prestige Aatrox skin cost and found:

TL:DR Prestige Aatrox costs you $139.46 AUD

The best deal for prestige points is the Blood Moon Capsule Combo at: 168.75 RP per PP (Prestige Points)

Ordinary Mastery Work Chests: 225 RP per PP

Mastery Work Chest Combo: 173.0769231 RP per PP

Blood Moon Capsule: 187.5 RP per PP

If you need 100 PP and it costs 168.75 RP per PP. 100 x 168.75 = 16,875 RP. Which means that, if you were buying the $100 AUD RP combo, $1 can get you 121 RP so 16,875 divided by 121 = $139.4628099 AUD to get the Prestige Atrox skin. Ridiculous right?