Personally I would have thought the reason for finishing a PPL in the states is obvious.
Portman needs about 30 hours now.
UK:
30 x £100 = £3000 (aircraft)
20 x £20 = £400 (instructor)
+ umpteen landings...
total: around £4000
USA:
30 x $70 = $2100
20 x $25 = $500
all landings free..
total: $2600 = approx £1300...