Amazon happily collect Sales tax (we call it VAT or TVA) in Europe. They also manage the complexities of exports to non-EU countries and the differences between rates in different EU countries. Example: While I lived in France I paid French TAV on purchases from Amazon.co.uk when goods were delivered to me in France but UK VAT on purchases I made on the same site that were delivered to friends in the UK.
So - this is not something they do not know how to do or something with prohibitive costs.