As I understand it in the US the taxes are added after the displayed price, how much would that be in the end? In Europe it seems to cost €399 which is 30% more!
In the US taxes are a combination of city, county and state. For example there are often city ordinances adding 0.25% to the sales tax to support something or other. For example here are the sales tax rates in California by city or county, varying between 7 and 10%: http://www.boe.ca.gov/cgi-bin/rates.cgi
The voting is ludicrously complex (Americans like things that way!). For example many bureaucratic positions are elected. Consequently when people go to vote, they have to vote on a lot of things. Here is the California voter guide: http://voterguide.sos.ca.gov/pdf/
It starts out with Obama and Romney, heads into Senate & Congress, then the state senate & assembly, then into county positions and finally city positions. Then there are propositions for the state, county and city.
After that digression, the California sales taxes for purchases made in person are based on where the store is. Except for cars which are based on the purchaser address. For distance purchases (eg internet, mail order) they are based on where the business decides its tax presence is. Amazon for example took that into account when deciding where to have their presence on opening in California and actually got some tax concessions from the "lucky" cities (yes corporate welfare is well established in the US).
For sales where the purchaser and seller are in different states no sales tax can be charged. Most states then have a provision requiring the purchaser to report these purchases and pay a "use" tax whose rate is identical to the sales tax rate. As far as I can tell many do not report this.
Sales taxes in the US vary by state. Further, not all merchants will charge sales tax for either state when shipping between states -- this generally depends on whether the merchant is considered to have a business presence in the purchasers state.
