For excelling at a single discipline, I was thinking closer to "Job Points used for all classes". I was also thinking that the more Job Points that have been used, the more expensive abilities cost for all disciplines.
If say, the average player reaching end game would have amassed enough job points to acquire most of the abilities of a single skill path for the one class (i.e. if Gladiator had a protection skill path, a combat skill path, and a leader/captain skill path).
A player may decide that leveling all his/her other classes to 50, doesn't want to specialize in that class, decide to invest those job points toward Gladiator to finish out the remaining skill paths. Trying to master all the skill paths the Gladiator had available (or the equivalent of skill paths).
I started typing up a crazy amount of text, but went off on an insane/zany tangent.
edit: appending.
The scaled cost for abilities is intended to reward players who specialize sooner than players who seek to max all classes eventually. Players that continue to repeat primals, dungeons, caravans, faction leves, hamlets, material grinding, going for achievements, or spirit bond parties would continue to have another type of progression. Or even having that level 49 recently turned level 50 stick in the level-up party for a while longer, because it's still advancing.
A player may eventually unlock all of the skill paths for all disciples.
From a leatherworker that can apply an enhancement such as "increase movement speed by 10%" to any boots they make.
An armorer that can apply the boot enhancement to "increase bind resistance".
A miner that can mine the corpse of a golem or other rock-like creature.
A botanist that can chip some wood out of that Guardian of the Grove/Forest/Treant.
An archer that sometimes does not consume arrows when firing a shot.
Things here and there and everywhere (in addition to the usual stat enhancers like +8 healing magic potency or +2 control).
When that crafter (or gatherer) is going toward their achievement, fulfilling quotas, or just looking for profit, they're gradually becoming master craftsfolk, producing higher quality products with greater success.
This may not stop a player who ultimately wants to max out all classes. It may aid a player who insists on playing one class more than others and being able to perform it statistically better than non-specialists sooner. The scaled cost for abilities is intended to grant benefits sooner to those who specialize, but since there is no need to reset,