extra costs in UK
All training aircraft in the UK, have to be maintained to Public Transport Certificate of Airworthiness, but not in the USA, or most other EU countries.
Most aircraft spares are more expensive in the UK. Maintenance labour costs are higher in the UK.
Both new & used aircraft cost more to buy in the UK, than the USA.
On the whole instructors in the UK, for both PPL & CPL, are paid more than their counterparts in the USA. (One could argue that they should be, as they have paid more for thier training, in the first place.)
All flight training in the UK carries VAT at 17.5%. Sales tax in the USA varies from state to state, but it is always a lot lower than 17.5%.