Is there any mathematical system behind champion IP/RP costs?

I had never really thought about it before, but the champion IP/RP costs really make no sense, and are seemingly totally arbitrary.

IP 450 +900 : 200% 1350 +1800 : 133.333~% 3150 +1650 : 52.38~% 4800 +1500 : 31.25% 6300 Total increase: 1300%

RP 260 +325 : 125% 585 +205 : 35.043~% 790 +90 :11.39~% 880 +95 : 10.8~% 975 Total increase: 248.21% Not that it really matters, but I was curious if I'm missing some mathematical system in deciding the RP/IP prices, in relation to each other or themselves.