Seems a decent price for all 4 series (25 episodes) of Maid Marian and her Merry Men. Digital download from the BBC Store. Not available on any streaming service (as far as I'm aware). DVD is £25 on Amazon, £39 on Zavvi.
Maid Marian and Her Merry Men Complete Series 1-4 Bundle £10.49 on BBC Store (Digital download)