I'm glad when we have Peak/Off Peak differentials such as:
London Terminals - Manchester Anytime Return £332, Off Peak Return £82.40
Northampton - Euston Anytime Day Return £57.40, Off Peak Day Return £27.50
Dover Priory - St Pancras Anytime Return £84.10, Off Peak Return £41.30
Glasgow Queen St - Edinburgh Anytime Day Return £23.30, Off Peak Day Return £12.60
I'm sure others can come up with more examples.....
On longer distance routes the Off Peak Return is generally regulated and can only increase in price by a set amount each year. Greedy TOC's have taken it upon themselves to increase the cost of Anytime fares disproportionately as they know many travellers on log distance trains at 'peak' times are business travellers and will pay whatever it costs!
In the south east it's generally the Anytime Day Return that's regulated which limits the opportunity for large differences between the Anytime and Off Peak fares.
It's nothing to do with loadings - the basics of the fare structure was out in place when the railways were privatised. TOCs have pushed the boundaries since privatisation and I dread to think what some fares would be if regulation was scrapped.