Dude, your uncle's shop loses money...
That's actually a bad thing.
It may be good for you, but bad for the shop.
They are called staff discounts. Doesn't really lose money, typically they buy in products about half their value. So they're basically still making profit. You wouldn't sell something for the same price you bought it for. A mere 5 bucks per card on an infrequent basis won't affect the business.