It’s not all doom and gloom.
Camelbak spares are chap as chips ($10 for tubes, cleaning kits, bite valves in packs of three).
Most oakley and camelbak hardware is the same digits in $ as £. There’s a few states where there is no sales tax (Oregon is one I think Delaware, Montana & New Hampshire are the others).
Outlet malls are totally bargainicious. Of the many hundreds that there are, Premium outlets seem to be the best stocked.
A Costco card give you access to their stuff, which in the US is properly cheap – my gopro hero2 with wifi pack was $130 a few years ago.
For general outdoor gear dicks sporting goods is ok, but rei is better, despite having a reputation as a rip off palace amongst locals. Rei membership seems to be worthwhile. For some reason, proper Lake District approved waterproofs are stupendously expensive in the states – that’s if you can find any.
If you have children then kids clothes are very cheap.
Sure I’ll think of more.
Oh, yes uggs. Not really bike related, but if you or anyone you know has a penchant for Australian cattle rancher footware then uggs are almost a sensible price.