The cost for upgrading the purchasable card level seems to quickly outpace the cost for the price decrease upgrade. The card level upgrade cost is 4 billion, and the cost decrease upgrade is 163 million, and when I have to purchase a card, it still only cost 1 coin. The level progression of the cards in the game also feels a little slow to me. My cards are level 34 while the cards I'm facing are 30/31 ecluding the commander card.