Beyond zones 1-9 the daily and weekly caps for contactless PAYG are usually set at the same rates as the outboundary travelcards (Anytime, Off-peak and Weekly) to zones 1-6. This is because using contactless is marketed as a convenience rather than value for money. Note that there are exceptions where Oyster is also available because of restrictions with the on-card system.
What has recently been spotted is that Great Western Railway increased the prices of their day travelcards from Iver to Reading (including the branch lines) by between 10p and 30p, but did not ask TfL to change the daily PAYG caps. This means that from Reading the travelcard prices are £59.60 Anytime and £28.00 Off-peak, while the corresponding caps are £59.40 and £27.70.
This means that for full-fare adult passengers PAYG really is the best way to travel to London for a day. If you don’t use other transport in the capital enough to trigger the cap then you’ll only pay for the fares, and if you do cap you’ll still save on the day travelcard price.
There are also other benefits too. A day travelcard is only valid for one return journey between the origin and zone 6 but the daily caps apply for multiple journeys. The caps also apply to people starting in London and visiting Windsor for example. No faffing around buying a travelcard and a separate ticket from the zone 6 boundary.
And most importantly for Twyford and the Henley branch, you can travel via Reading on fast trains without paying the usual premium as long as you don’t leave the station at Reading. What’s not to like.
Finally, it looks like this change occured in the June fares revision. It was not corrected in September, so it’s likely to continue until at least next March. What happens then is anyones guess, so make the most of it while you can.