Consider the following:
Stamford - London King's Cross (changing trains in Peterborough) costs:
£96 Standard Class Anytime return and
£129 First Class Anytime return
Stamford - Birmingham (direct train) costs:
£49.50 Standard Class Anytime return
£144.50 First Class Anytime return
Why the huge disparity between Standard and First fares on the two routes? The Stamford-London journey sees the fare set by the East Coast franchise operator, whoever that may be at the time, whereas CrossCountry set the fares for travel between Stamford-Birmingham.
Under normal circumstances, most train operating companies (TOCs) increase the walk-on First Class fare by around 60% of the Standard fare. First Class generally affords the user a wider seat, which is aligned with a window, a table lamp of sorts and generally 2+1 seating throughout. Most TOCs provide an edible gratuity, too, though ironically not CrossCountry aboard its Turbostars.
Goodness knows what calculation XC has used when working out its Turbostar First Class fares. It certainly is not a 60% on Standard - more like 292% and not a free packet of biscuits or item of fruit to be had.