Or £8,800 if you choose the "Great Northern and Thameslink" only one rather than the "Any Permitted" one. The former lets you travel on the same services as the latter as well as intercity services operated by LNER. They are somewhat quicker of course by virtue of not stopping anywhere after Peterborough (if they even stop there in the first place!), but as Thameslink services continue through London instead of terminating at King's Cross their slower time to get to King's Cross can pay off with a shorter overall journey by virtue of not having to change trains (for a number of people, this can also mean not needing to pay for the tube either - bringing it down to £7,388 year).
Now undoubtedly £7,388 a year is a significant chunk of cash. But to be clear, Peterborough is very much on the edge of the commuter belt at 60 miles from London. A more typical 'commuter belt' origin on that route would be somewhere like Stevenage, Welwyn or Hatfield - which come in at £4,224/year, £3,300/year and £3,076/year respectively.
Now undoubtedly £7,388 a year is a significant chunk of cash. But to be clear, Peterborough is very much on the edge of the commuter belt at 60 miles from London. A more typical 'commuter belt' origin on that route would be somewhere like Stevenage, Welwyn or Hatfield - which come in at £4,224/year, £3,300/year and £3,076/year respectively.