If a purchase was unintentional and very large ($4,333) a refund should be offered. This feels like common sense to me.
That's a large amount of money to lose. Providing annoyingly bad customer service to people and then signing off with "Warm Regards" is likely to make enemies of customers.
Edit: Somebody mentioned that Taleb might be bullshiting about there being no confirmation, however, to be honest, I still think at this price level, customer support should be able to refund purchases. Keep your customers happy (and they will eventually purchase upgrades from you)!