If you buy them in bulk for employees they get progressively cheaper. It also matters how many customers you can serve vs how many you have and what you spend to get one customer into your store. If you spend 500 per day to get 100 customers into your brick and mortar store you can also give/spend 500 in discounts to get 100 more. If only 60% redeems the card the other 40% is profit. ETC

Un-redeemed GC aren’t profit. You can’t book the revenue, rather the balances count as a liability (because you owe all the random cardholders valuable goods/services) and, at least in my state, after a certain period of inactivity, you’re obligated to give that money to the State as unclaimed property. Google “escheatment”