Ralf said "This Must be a Joke. From Ken Livingstone's new propaganda pamphlet 'London Loop, the new magazine for Tube and Bus users'".
As I said in his comments you can do anything you like with statistics really, so in some sort of way, we are among the cheapest fares if you use Oystercard pre-pay and if you base cheapness on potentially how many stations you can travel through for your £3.50 for a single. (yup three pounds 50p for a single ticket - wot a bargain!)
We just happen to have a lot more stations packed into our miles than other countries.
London's Tube system covers a comparatively small area for the number of stations that it has.
Incidentally, has anyone come across this London Loop magazine (or rather London Loopy if it thinks we're buying their mad cheap London Underground fares argument)?