Board Thread:Questions and Answers/@comment-16190015-20140602051933/@comment-71.246.99.184-20140704162223

It's purposely designed to failed, so with the amount of time wasted farming coins, some will have no choice, but to use crystals, if they really want to upgrade that particular treasure. Crystals can be earned during events or leveling up, but it will take quite some time, to accumulate enough amount, just to upgrade a single treasure. Angel's Holy Feature from +5 to +6 uses 35 crystals. If you were to gather crystals just by leveling up, it will take forever to do so because each level up gets you 1 crystal and to get 35 crystals, means you will need to level up 35 times just to upgrade that single treasure. For some, this method is a pain in the a$$, therefore they buy crystals instead and that involves real money.

To put in simple terms, they game want you to upgrade your treasue by using real money.