So I played SoG for a few days now...
How does spending money for crystal in game compare to spending money on BCY to buy blockchain cards? (in terms of game play)
you cant buy crystals, you get them when crystalizing not needed cards. You can buy Gemz. Gemz are used to refill stamina and also to buy cards.
what about the power of "epic or better card" vs blockchain card?
There are rare, epic and Legendary blcockhain cards. Difference is that blochcain card is Golden so 2 times fused. You need to draw 4 same cards and fully upgrade them to be abel to make 2 fuses and get a Golden card.