In order to answer this question fairly you have to take like for like.
In my case I wanted to travel to Newport S.Wales a round trip of 72 miles. My car does about 35 to the gallon so that would be just a tad over 2 gallons which equals to £5.54 a gallon taking into account in my case £5.30 bridge toll equals £16.38 (not counting parking, a percentage of cost including insurance, servicing, wear and tear, appreciation, etc of which you could add several pounds more !)
The Train fare I paid was £7.60 I think that says it all.
You have to be serious and go for cheap options like travelling off peak, but if you like me plan your journey you can save pounds on the train, do your homework first.
Of course if you go for peak times, express trains,main commuter routes, first class travel, like probably the high costs you mention possibly represent, I am not at all surprised.
My city and Glasgow is a round trip of 800 miles so I would use about £130 of fuel take about 20 hours to drive (the train gets there and back in 12 hours saving 8 hours in time !) not counting actual stress involved which should be worth something.
The Train Fare would be £91.50
I have done some research into this and being an accountant I think I save money by going by train, at least if plan the journey and allow the unexpected like you get sometimes.
I can only speak fo myself and I think you could plan better ask for special offers next time, you can save alot by paying in advance too.