Opinion needed - how can a store sell silver at 15% less than market price

So, someone I know has a small function at their home and they went to a local silver store that is know to their relative to purchase 30 small silver cups.

I was talking to them today and they were mentioning about how their relative could fetch them 15% discount over the market price for silver as they got the cups in wholesale. I was baffled and couldn’t understand how the metal price can be discounted by 15%!!

Can someone help me understand if it’s even possible?

The only reasoning I can come up with is obviously the silver cups have very less purity. Is that it or can shops actually sell genuine and sterling silver cups at 15% discount on silver metal price when purchased in wholesale?

PS: I am talking about metal price billing and not making charges and wastage. They billed the silver metal price 15% less and then added Rs. 3000 per kg to final bill for wastage and making charge.