I believe it's good to keep track of your earnings in the game. I've been playing the game for more than 3 years. From my experience, the best to do in situations were prices go down is to increase your deck by buying cheap cards in order to play them. I believe that we will reach the cheapest prices a couple of weeks after the general sale of chaos starts. Once everybody opens their packs, they will drop a lot of cards on the market and prices will go down. That's a pretty good time to go shopping :-).
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