I did not know that
"iPad purchases are limited to 2 per customer and must be purchased with a Credit Card or Debit Card only."
"A Ha!" Says I. Cash is legal tender, they *must* take cash. Or not.
There is, however, no Federal statute mandating that a private business, a person or an organization must accept currency or coins as for payment for goods and/or services. Private businesses are free to develop their own policies on whether or not to accept cash unless there is a State law which says otherwise.
I would have bet a zillion dollars that businesses are required to accept cash. Learn something new every day.