No, the "vanilla" releases of the first series are around £15.99 for each of the four volumes. Each volume had three episodes and no extras.
The complete series (which has all the added and bonus material) is £70 from the same site.
Of course you can buy them cheaper elsewhere, but HMV will charge whatever people will are prepared to pay. If people can't be bothered to shop around and pay less, too bad.
But if I have got this completely wrong, and you can get the entire first series for seven quid, please tell me where!