Lots of people here are complaining about paying VAT for S1, what makes you doubt that Bitmain has VAT?
I sent a RSA token (banking token) to a company in China valued at USD100, they have to pay RMB150 to get it from DHL.
They do not pay VAT on foreign sales.
For units they recive for repair they do not pay VAT to recive it aslong as they can provide any form of documentation that it is service and ship it out of the country again in x days (not sure on the timeframe of return).
If not within timeframe they pay VAT, then as they ship it out of the country with same value/adress as shipped it to them they get the VAT back.