Heathrow Express has had a reputation for being expensive since it launched. A few years ago, the service tried to rid itself of this image by launching £5.50 one-way advance tickets.
These were a good deal. Whilst you had to book well in advance, this wasn’t an issue for anyone who had already booked a flight. You did NOT need to commit to a specific train, with the flexibility to take any service on the day you booked.
Given that children travel free on Heathrow Express, it meant that a family of four could travel from Paddington to Heathrow for just £11. There’s certainly nothing expensive about that. If you had a suitable railcard, it could be even cheaper.
The £5.50 tickets appear to have been quietly withdrawn.
The website now shows that the cheapest Advanced Purchase Single ticket is £16.50. This doesn’t seem to be an error, as the website elsewhere says “Travel with us from just £16.50”.
I don’t know how popular the £5.50 tickets were. Perhaps the operator is gambing that selling a few at £16.50 will be more lucrative than selling a lot at £5.50.