I do not know how other Greek suppliers do it, all I know is that MMVapors is doing everything according to Greek law.
And you are welcome to have your order shipped as a commercial export so you do not pay for VAT. But as stated before the end-cost will be a lot higher.
The "commercial" designation you describe sounds like something that is being purchased for resale, at least that is how US Customs interprets the term. What I would be purchasing is
merchandise for personal use.
"VAT on imports and exports:
For the purpose of exports between the Community and non-member countries, no VAT is charged on the transaction and the VAT already paid on the inputs of the good for export is deducted - this is an exemption with the right to deduct the input VAT, sometimes called 'zero-rating'. There is thus no residual VAT contained in the export price." (Quoted for the site below)
General overview - European commission
I getting my information about international online purchases directly from the US Customs site.
Internet Purchases | U.S. Customs and Border Protection
ETA: MMVapors has to be affixing a customs declaration of some sort on the package (From the US Customs site):
"Note: It is important to know that foreign shipments that are not accompanied by a U.S. Customs and Border Protection declaration form and an invoice may be subject to seizure, forfeiture or return to sender."
"Hint: To speed a package
through CBP examination at a port's International Mail Branch, the seller should affix a completed CN 22 or CN 23 (U.S. Customs and Border Protection Declaration Form) to the outside of the package. This form may be obtained at local post offices worldwide."