I fail to understand why I can be sat next to someone in the same train carriage who pays almost double. I am told it's 'supply and demand' which is some law of economics that has been bashed into us by economists. Trains travel fixed distance, same fuel costs, same staff costs, so why does everything get more expensive??
I'll try to explain the theory of "dynamic pricing" used for "Advance" tickets: the operator tries to sell a set number of low-price tickets well in advance to cover costs long before they have to pay out much towards running the service, then most prices increase in an effort to manage relative demand by making quieter trains more attractive to people who are a bit flexible about when they travel (because busy trains must dwell longer at stations and generate complaints about overcrowding), then in the final phase if any train is too under-occupied, it should be priced more cheaply again. All the time, the walk-up fares like Anytime and Super Off-peak act as a cap on prices and cater to people who don't tell the operator in advance when they will travel.
If there was no dynamic pricing in operation, people wouldn't be rewarded for booking early and helping the operator manage usage. Because the regulated fares are a political topic, I suspect it would probably mean they'd be a bit low for peak and shoulder times and current overcrowding would seem like the good old days.
As far as I know, the precise details are trade secrets, but that's the gist of it.
http://mcafee.cc/Papers/PDF/DynamicPriceDiscrimination.pdf is a more scholarly 40-ish-page review of it, based on US airlines.
In theory, train operators could use the early numbers of Advance tickets sold to vary the numbers of carriages on different services, so you'd see prices rise slowly, then drop each time more carriages were added, but the difficulty of varying formations (even locomotive-hauled services seem basically fixed-formation in service now) and the low numbers of "spare" units on intensively-worked UK railways means I don't think it happens often for trains here.
. I would go by Nat Express, but that means going into the city to come out again, plus an a*se numbing 2hrs 20 mins on the coach as opposed to 90 mins train time. Thanks to the dumb Tories, when they got into power in 2015, they took out the three mile bus lane at the end of the M4 that petrolhead voters moaned about. This created new 3 mile jam and has increased coach time to London!.
