Does anyone know the total cost all the Paladin's spells and abilities?
 

Including of you'd spec in all trees, so you buy all the spells you get from the trees.

As in, cost in money? Nope.

I know that Paladins (and Warlocks) used to pay 10% more per ability than other classes, to offset the "free" mounts/training. Not sure if they altered this or not.

Around 830g 15s 68c

I assume it would vary a bit by class...

By level, they're flat costs. Everybody pays the same price, for example, each level 50 spell. Except that Paladins and Warlocks used to be charged 10% more than other classes. The real price difference comes in with how MANY abilities+ranks your class has, and at which levels you get the abilities or new ranks.