This appiies not just to railways but especially to airlines and also thatrical perfornces. lastminute.com exploits this system.
Airlines are an excellent example. Some flights I've been looking at daily have been ^65, ^75, ^85, ^95, ^105 and today back back down to ^85. Funny considering it said "only 2 seats left at this fare" yesterday at ^105 ... those two people making a booking actually triggered a price reduction!
Back to the railway, I know
NXEC▸ were lowering prices several years before handing back their franchise. They initially denied it when I contacted them, claiming I must have looked at a different train