An important question, so I'll provide a detailed explanation.
TL;DR It's our actual costs (or less than our actual costs). Details below. : )
For me to ship to the EU in a "VAT friendly way", we have to put our dice on a dedicated freight pallet aside from the one to the USA; when we do that we nearly double our freight costs due to new charges for a new pallet on a new ship. We then pre-pay 20% of your dice value in VAT, with service fees (we pay that for you). We then have to pay the fulfillment company to de-palletize 40+ SKUs, store it, input into their computer systems, schedule time, pay their employees, buy packaging/labels from them, contend with Pick & Pack fees per item (imagine!), and then pay what is pretty expensive base shipping rates (usually starting at 8-9€ - much more costly that here in the USA where it starts at $5-7 USD with no VAT or Pick & Pack fees and all I need to pay for is packaging). Finally, we'll be doing all of that with the US Dollar (the weaker currency) which needs to be converted to Euros or British Pounds (the stronger currency), at an additional loss of exchange fees. *PHEW!* : )
"Why do it then?"
It's better for you, and you asked me to. : )