My 12 years old kid loves the game. He has like hundred of hours of playtime. According to him, the game is really fun to play and fast paced. Good music.
The graphics are really good and the art is gorgeous. you can buy characters and their costumes with in-game currency or with real money. My Child has spent about 100 dollars on it, but spread in about two years. But you can play without paying, it will depends on your wallet.
same with all the goodies that your kid might want, figure pvc toy, pillow, posters etc... those can cost a lot.