Summary
Commute cost should be estimated from your actual weekly pattern, not from one single fare. Full season tickets suit frequent peak travel, Flexi Season can suit part week commuting, and PAYG caps may work best in London and some South East routes.
Definition
Rail commute costing means comparing the realistic ticket products for your journey and travel pattern. A weekly, monthly or annual Season Ticket can be better for regular peak journeys between two stations. A Flexi Season Ticket gives any 8 days of travel in 28 days and can fit hybrid workers. Pay as you go with contactless or Oyster may be better in London and some surrounding areas where daily or Monday to Sunday caps apply. For an area check, price the route with National Rail tools, multiply by your expected commuting days, and compare it with season, Flexi and PAYG options before adding local bus, Tube, parking or cycling costs.