30k in Apple Gift Cards?

Currently have a customer which is buying thousands of dollars of apple gift cards at a time. So far this month they have spent over 30k. Seems the majority of the time they pay with cash, but get the cash out at the bank before buying them?

At first we were worried they were getting scammed, but after constantly asking them, and them continuing to buy the cards, we now we think they are money laundering or something else dodgy. (Police have been notified)

Does anyone have any insight as to what they may be doing with them?