[T]he Raspberry Pi Foundation had intended to get all its manufacture done in the UK; after all, we’re a UK charity, we want to help bootstrap the UK electronics industry, and doing our manufacturing in the UK seemed another way to help reach our goals.
We investigated a number of possible UK manufacturers, but encountered a few problems...
[O]ne cost in particular ... really created problems for us in Britain. Simply put, if we build the Raspberry Pi in Britain, we have to pay a lot more tax. If a British company imports components, it has to pay tax on those (and most components are not made in the UK). If, however, a completed device is made abroad and imported into the UK – with all of those components soldered onto it – it does not attract any import duty at all.
Res ipsa loquitur.