that 45% means the cost of going up each level
the costs more than dubble at each level so a 15 set is more than 2X the costs of a 14 and that happens every time form level 10 i think on and 10's are still a fare amount of gems / money so if a 13 costs you like $200 a 14 costs you like 500 and a 15 costs you like $1300 that is why when some one says i have some 14s and 13s and on 15 i say great keep it that way unless you are willing to sell your soul to evony.
I had to ***** my self for my star set.