It is a standard assumption that people don't buy things they don't think are worth it. It's not a bad nor even unusual assumption either - the very definition of people thinking that something is worth it is that they're willing to buy it. Without a gun to their heads of course - we mean voluntarily buy it, not taxation.
Thus some two thirds of the passengers on British trains shouldn't be there:
Only one in three commuters believes their rail fare is value for money, according to the passenger watchdog’s national survey.
Transport Focus, whose national rail passenger survey asked 27,000 passengers to rate aspects of their journeys in the autumn, said that the value for money scores reflected “patchy reliability” of train services.
While 47% of passengers overall felt they had paid a fair price for their ticket, only 33% of those commuting to work were satisfied with its value.
OK, we can argue about whether it's two thirds of commuters or only half of all passengers. But they don't think it's value for money - yet by the definition of the group being asked they must all be paying for it. Thus they do value it at what is being charged, or more, by definition.
What is happening here is the difference between expressed preferences and revealed such. That people do pay current prices shows that their economic calculation shows those fares are worth it. When someone comes along and asks whether we'd like the same thing cheaper of course we say yes.
Shrug, we think that 12 year old malt is terribly expensive and we'd much prefer it to be cheaper. But that we've a bottle of it on the shelf - some part of that bottle in a glass often enough - shows we think it worth the price all the same.