Neil Williams wrote:

It takes 5 mins to get one, and then you just feed a tenner into the
machine when the barriers say you are getting low.

...which TfL get to keep and earn interest on.


If you really want to pay for your tickets one at a time then you can
still do so with Oyster. Instead of putting 3 pound coins into the
machine and getting a paper ticket, you simply touch the Oyster card on
the ticket machine, select 'top-up' then put in the 1.50 then touch the
card onto the ticket machine again.

This way, you still pay the lower Oyster fare but you don't have to pay
in advance and lose your interest to TfL.