Why does Amplifying Tome still cost a bizarre 435 gold?

It's kinda a relic from when health potions costed 35 gold, and hasn't been updated in the couple AP itemization passes since then.

It's one of only two non-consumable items whose price isn't a multiple of 25, the other one being Negatron Cloak (and I guess Trinity Force too, but that at least has an excuse for using a bunch of 3's).