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No, you buy what you miss and combine them👌 if you wnt to unbind you only pay for what is not unbound from before. Read again😉

Given the unlock cost, the profit from selling reward cards will be minimal. On the other hand, the cost of unlocked reward cards (to max our cards) will be at least the unlock cost which is quite expensive.

In summary, maxing reward cards without relying on glint shop will be prohibitively expensive and unreasonable for most players.