Yes Captonian you're correct but equally not quite as competitive as FR at €17.50 return which was widely available...
To which you need to add the cost of getting to and from the airports, the value of your time, and the stress and aggravation. It makes the train cheaper in the end. I use trains on journeys up to 6 or 7 hours and often even more, I find it's invariably a more pleasant option, although it can appear more expensive until you factor everything in.
EK77WNCL we are nearly all on this site because of a love for, or an interest in, aviation. That cannot override the practicalities that your enthusiastic approach to what routes you think might be viable is making you overlook.
For example, I would love to see a service from Cape Town to Hawarden (Chester). It would suit me perfectly, I'd use it maybe six times a year, and so would some of my friends and family. Do the sums ........ it's dead in the water.