Dave Newt writes:

Likewise, how can a £1.35 fare be called "more expensive" simply
because there aren't as many stations you could go to than a £3.50
fare with a wider choice of destinations?

It might also be worth pointing out that the comparison is based
on cash fares in the other cities (for instance, in Helsinki, the fare
with the local Oyster equivalent is £1.05 (EUR 1.70)) which all also
include free bus/tram/local train transfers within 60 to 120 minutes.