Briefly speaking,
In my opinion 100 valor for 1 unbinder coupon is cheap for a high level player, especially 200+ since we can earn valor in dungeons.
How about low level players? They can do quests but they don't give much, some are time-consuming and even hard to do to some specific players without buffs or decent gears.
How about a 50 or 70 valor unbinder coupon with for example: Under level 100 restriction?
Just crossed my mind.