The prices to level units are super high, so to get to level 60 it would take hm... 475,625 gold if my math is correct
This feature is there for fully maxed out players. To give an option to drop something like 40k to get your new Dragon slayer to competitive level 18-20, so you can spend your time in large scale PvP instead of grinding that one unit as you would in the first couple of week of play.
And don`t worry guys - our approach is - if something doesn`t work and players are not happy, we change it right away.