The reason it doesn't make sense to me is that there are clearly engineers in the UK who are as talented as the average engineer in silicon valley and are unwilling to move to the other side of the world. There are also many many many companies in the US that have offices in the UK. Given that UK engineers appear to earn no where near their US equivalent I would have thought there would be a strong incentive to hire more in the UK and therefore drive up wages rather than continually pump money back in silicon valley.