UK train travel prices, why are they so non-sensical?

For example, I was looking at getting a train from Leeds to Glastonbury on the day the festival opens and the first journey that came up was �160. If I bought separate tickets for each leg of the exact same journey it was �92. After exploring other journeys I managed to find a way of getting there by train in 6 1/2 hrs for just under �35! This seems very odd to me, does anyone know why the prices vary so much?