Why do some runes cost up to 2k IP?

I was going to try out LS quints on Yasuo, since Phreak said they are the best at the moment, but then I saw that 1 LS Quint costs 2050 IP. I barely have enough for 2 of those after a week full of games.

I know that majority of expensive runes are either gimmicky or useless and noob traps, but I feel like their price should still be toned down a little.