Problem is the vast majority of customers only look at the headline fare.
If the headline fair is £10 more they say I'm not paying that I will book pikey for 99p. Then when they get all the way through to the payment part of the pikey website they say "oh look Jet2 was actually £5 cheaper-never mind I am on here now and can't be bothered to enter all those details agian I will just pay the £5 extra"
It is how it works and untill that stops the system just won't change.