At the end of ladder 1, most high runes, with the exception of like one or two of them had a 1:1 trade value...

vex:
SIlence - Dol + Eld + Hel + Ist + Tir + Vex
BOTD - Vex + Hel + El + Eld + Zod + Eth
EXILE - Vex + Ohm + Ist + Dol
HOTO - Ko + Vex + Pul + Thul

Ohm:
BRAMBLE - Ral + Ohm + Sur + Eth
CTA - Amn + Ral + Mal + Ist + Ohm
CHAOS - Fal + Ohm + Um
DOOM - Hel + Ohm + Um + Lo + Cham
EXILE - Vex + Ohm + Ist + Dol
FAMINE - Fal + Ohm + Ort + Jah

Thats three good runewords with vex, and 5 good runewords with Ohm. It would be utterly illogical for vex to be worth more then ohm.