Why only 8 episodes?

[YourFutureMuse]

Oh I know the box set things really annoy me... Like you pay the same price for series 1 with only 6 episodes and series 2 with 10 and you can also pay the same price for something like Grey's Anatomy with like a bizillion episodes.. That is strange..

And that 8 would be good if that were the case but I don't think it is, I think 10 are needed for a developed storyline. For example in series 8 the nightingale plot could have done wth those 2 extra eps in my opinion