Trains from Hull to Berwick-upon-tweed?

I'm looking for a train that goes from hull to berwick-upon-tweed. I went on the national rail website and it said that an adult single was �60!! As this is way too expensive, i went on Virgin Trains and it said that you can get a cheap single for �12. Are there any hidden costs involved because it seems a bit odd that it is so cheap compared to other prices?