Ouch !! that would hurt. Yes Air Freight is not cheap. Just have to wait for a UK supplier eventually I suppose ? Or are these American made only ?
I'm sure they're made in China, Taiwan, etc. as 95% of the alloys on the market are. No reason to think that means the quality won't be any good though. If a UK company was to import these in reasonable quantities, there's no reason to think the price would be crazy - not the cheapest I'm sure, but not BBS money. With a lot of US rims, they're imported one or two sets a time to the UK, so the prices end up too high.