£2,589 for an all-inclusive 50-day bus-cruise, even today, doesn't seem that overly expensive. (~£50/day).
So it's not just inflation, it's "that used to be cheaper".
I guess on the flipside, travelling by plane in 1957 (or even 1974), would have been much more than £2,589.
> travelling by plane in 1957 (or even 1974), would have been much more [expensive]
Not to mention a lot more dangerous.
The problem is that the suspension would not be great back then.
About twice as much. https://www.indianairmails.com/ai-bombay-to-london.html 1948 price was £141 one-way. This likely did not change much in the early years.