Not scientific but randomly picking a date in April the cheapest NQY/LGW flight is a couple of pounds cheaper than the cheapest standard rail fare. Using the traditional ( for those with long enough memories) comparison to the First Class fare it is about half the price.
From an airline economic point of view I have long laboured you don't have to compete with the locos if you are the ONLY person offering the ability to fly to a destination with no competition.
I would rather have to provide for 10 passengers at £200 than 60 at £25!