PayPal order form doesn't verify location for shipping costs

I've been doing some maintenance work for the lady who owns this website. So far its been good, but I really don't have much experience with these order forms.

She noticed someone from within the USA made an order and got through checkout with her location set to Australia, there for getting the item cheaper thanks to the shipping costs.

TESTING: The cost applies properly when selected, but there doesn't seem to be anything stopping someone simply choosing a different location. I've tried ordering different combos of plate/location etc. Different browsers don't make a difference.

The form is the order form on this website : http://ift.tt/2poklU4

Am I just missing something simple here, or is this a limitation of using a form like this?

Thank you.