If they can't be bothered actually doing currency conversions (and ripping off those who pay in EUR)...then I wouldn't even entertain them.
something I intensely dislike as well, but, in fairness there's very few that do (actual currency conversions).
If I can, when paying, I'll try and pay in US$ to see if it works out cheaper.
Add to that, there's very little between the two at the moment.
EDIT// the Euro price includes 19% VAT. Dont know if they charge that to all customers (? they a German company & I'm in Germany)
Paying in EUR would mean you pay 6EUR more than you would if you paid in USD - Yeah, in fairness it's not THAT much, but..in reality, there is 0 need for it when there are a plethora of payment modules that just do the price for you (or if you set a single currency, and have Paypal as your provider...they do the work for you) - there is really no excuse - I'd understand it if they had to keep changing it manually due to fluctuating rates..but we all know this is not the case.
In regards to your edit, they are charging me 20% tax (as per UK rates)
included VAT (20%): £ 11.70
included VAT (19%): £ 0.00
The total for Pro: £70.20 ($87.20)
I think the moral of the story is....if you want it...find somebody in the USA to buy it for you...or be prepared to pay more than your american counterpart.