Depends what time of day you travel.

Just checked online and weekday London to Manchester (163miles) single cost £120 peak down to about £60 off peak. Just over 2 hours journey time.

Coaches are a lot cheaper but slower, average £20 but a 5 hour journey.

Same applies here in Ireland. I find if you have time to spare coach is a lot cheaper option. I often recommend my Warmshower guests to take the bus from Dublin to Cork rather than the train. Often it's easier to take your bike on the coach as well.