Co-incidentally "Rail" magazine has recently published comparative figures for longer distance "commuting", as follows:-
Norwich to London £29 ; Anytime return £93.10
Peterborough to London £26.20 :Anytime return £87
Bristol to London £42 : Anytime return £169
Manchester to London £53.40 : Anytime return £279
However, the sort of executive who could afford to commute from Manchester or Bristol might not be making 230 journeys a year (meetings elsewhere, foreign trips, essential golf tournaments etc.) which would reduce the discount.