Blue essence for buying champions

First of all, sorry for my English because it's not the best.

I have a question for people with PBE account or RIOT emplyoees... I saw that champs in future won't be able to purchase with IP but with blue essence and I want to know how much will champions cost ( I mean will ti be for example 450 blue essence for Ashe and 6300 blue essnce for Zed ) and also when u change IP to blue essence how much it will be worth ( Example: 1 IP = 1 Blue Essence or more or less ) ?