A good rule of thumb is to never go back to a purchase page (even on other sites they say not to refresh or resubmit). But I have reported this to a programmer and they will be looking into this as soon as they can. The ticket will of course take care of the actual reimbursement and duplicate purchases.

I have confirmed that the Boutique is coded as such to where if you attempt to refresh or use the back button, your browser will display a warning not to do this as it may cause the transaction to repeat. For example, Firefox says "To display this page, Firefox must send information that will repeat any action (such as a search or order confirmation) that was performed earlier." As I said above, it is a good rule of thumb not to refresh on a purchase page unless you wish to repeat the purchase.

However, the programmer was able to see that the same warning does not display for the cash shop hustler. So they are going to fix that.

The hustler has been fixed to throw a warning when you attempt to go back or refresh. Locking this up!