That is just untrue. A base Mac Pro is £5,499, an XDR is £4,599 and the stand is £949. So £11,047 including VAT or £9205.83 excluding VAT. In the US, a base Mac Pro is $5,999, an XDR is $4,999 and the stand is $999. So $11,997 excluding sales tax, which is £8,993.07 meaning that the difference in cost is £212.76 or 2.3%, which is more in line with the small extra profit margin Apple usually adds for markets outside of the US in order to factor in currency value fluctuations.
I would be very surprised if any person in the market for a Mac Pro, neigh, any grown up in the UK, would struggle to understand the concepts of sales tax or VAT so it seems you are just out to complain and be negative for no apparent reason.