The payment is not guaranteed; i.e. it is not interest and does not generate an APY. If it's more than $10, it's a bonus:
(f) Bonus
1. Examples. Bonuses include items of value, other than interest, offered as incentives to consumers, such as an offer to pay the final installment deposit for a holiday club account. Items that are not a bonus include discount coupons for goods or services at restaurants or stores.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.