Researching this fare for a visitor we are expecting and I see two options, one for £39.20 restriction code 4A and one for £47 restriction code 7B. He will be leaving Stansted around 10am, looking to return around 4pm both on (different) weekdays. On the face of it the cheaper fare appears to have fewer restrictions, indeed 7B would appear to exclude departing Liverpool Street at the time he will be travelling on the return journey. Envisaged route is Stansted Airport-Liverpool Street-London Bridge-Dartford. Am I missing something?
No, 4A is indeed less restrictive than 7B. However better value than a through Off-Peak Return is a Stansted Express Advance in both directions (available from the Greater Anglia website) and then Oyster or contactless from Liverpool Street to Dartford. Stansted Express Advances are valid on any train on the day they are issued for, and if you book them sufficiently far in advance, they can cost just £7 single, i.e. £14 return.
If you combine that with an Off-Peak Oyster/contactless fare from Liverpool Street to Dartford for the way out (£6.40) and an Anytime fare fom Dartford to Liverpool Street for the way back (£9.40, unless you can tap in before 16:00 in which case it's the Off-Peak £6.40), it's just £29.80, nearly £10 less than the through Off-Peak Return.
Still very poor value for money on a pence per mile basis, but somewhat more reasonable than the through Off-Peak Return.