My kids at least understand that "a dollar" can be exchanged for "good or services" and that if they want more they have to find another dollar. They haven't quite grasped that a coin isn't as good as a dollar, or that a 1 and a 10 are different.
A payment card would seem to either be magic (it always works!) or confusingly not consumed in its use but still not work again later (gift card).
My nine year old had a debit card attached a joint bank account. He could log in and see how much money he had. I gave him his allowance via a bank transfer.
A payment card would seem to either be magic (it always works!) or confusingly not consumed in its use but still not work again later (gift card).