I note that the price shown on the Steinberg Online Shop is listed as €599.99 for the full Pro version, or €99.99 for the upgrade including 19% VAT.
I would hope that the managers of the online shop would recall that they are legally obligated to collect VAT from customers in the European Union–but are not to collect VAT from customers outside the EU. And since the online sale specifically requires the customer to identify his or her country of residence, the online shop is fully aware of whether a customer is in the EU or not.
The non-VAT price for the full Dorico Pro 2 should be €504.19. The non-VAT price for the Dorico Pro 2 upgrade should be €84.02. You may want to consult with your tax advisors about whether you will need to refund over-collected VAT from non-EU customers. (You might also consult with the federal tax authorities–making the argument that making music is a particularly healthy activity, and thus should qualify for VAT rating similar to infant formula or milk. )
(I’m not trying to be a nuisance. Like many musicians, I have a day job. Mine includes fiscal compliance with tax requirements in 54 countries, including most of the EU.)