how does this apply to soul bound reward cards? these would only print dec but not increase card value ;)

Scarcity will still bring value. You assume everyone will burn cards. Some will, others will opt to hold them in an account and sell the full account with full sets of Soul Bound cards attached to said account. If the Soul Bound cards in said account have high play value and/or are scarce because many are already burned its likely such an account would be more valuable than an account without such things.