It depends. For example in EU, if you buy as private person then you are subjected to the same sales tax as the residents of the online seller country of reside

It depends. For example in EU, if you buy as private person then you are subjected to the same sales tax as the residents of the online seller country of residence. As a seller you can mitigate this by having your company registered in multiple countries (for example Amazon does this). If you buy as a company and can provide a valid sales tax id then the seller can exempt the sales tax at the moment of the purchase in case of exports.