How much Hp do Con Dyes give?

Plain and simple, with all the healer threads people say go WIT or go CON, i will proboboly go con but I want to know how much HP would I be gaining from +15 CON?

PM Astarothy, he always prefers CON and I am sure he knows very well how much it adds. He just doesnt want to tell us :D

On me - 99 , ES , +6 set robe , weapon + hp, 8 ap all to hp , all +con with dye +15 con , from dual 12% to hp - and on rose buff - 1 con is 760 hp for me