Unlucky, I have to concede that I had forgotten about Value Added Tax. Which as you rightly point out is not paid in the US. Last I checked the EU-Vat rate was a minimum of 15% (which ofc means it can be higher on gem services - not sure what category they fall under). They still vary from country to country, but not much to be done about that. This still leave a Eu residents with a relatively higher cost of gems (but not as high as claimed in my original post), but until BB explains their EU-US gem pricing policy we can guess all we want. I sincerely doubt they will ever explain it and to be honest I think they are just doing what everybody else is going (and getting away with) in using the $1=€1 conversion.
