I believe that there's a bit of a disconnect here.

500: The OP referred to assumed price in SWEK/GBP. The OP may be from SWE.

My "buyers %" is a low bid from experience in international art house auctions of objets vertu (as a curator) not a buyer.

From the propensity of governments to maximise their take I took a worst case assumption (that of compouned costs).

Customs agents of course set their own schedule of charges.

FWIW please read my origin (Oz) OK?