There are many journeys in London that are cheaper when avoiding zone 1, avoiding national rail and using buses for some or all of the journey.
Is there a good manual method of finding such routes or a general purpose route planner that optimises for price? I appreciate most people want to optimise for speed, walking time or number of transfers, however the alternate routes would not exist if there was no demand for them.
For example, Cockfosters to Upminster off-peak is £1.50 if avoiding zone 1, but £3.10 when taking the fastest route through zone 1. TFL Journey planner, Citymapper and Google Maps only suggested the £3.10 routes. Potters Bar to Upminster is only £1.50 extra (adding a bus journey to Cockfosters), but would be £7.70 or £11.80 with a train ticket.