Have to say my piece here, I dont mind paying for add ons concerning new content for games I have already paid for. However I dont believe there is much consistancy with the add-on material.
For example some times you can pay 800 MSP for something like Fable 2 add on Knothole island and it last an hr or so, and others charge less for more playing time and extra achievements.
Just think they should take into account what they are offering before they slap on the 800MSP tag.
Lionhead studios already said they were gona 'make up' to the fans with the next Fable instalment, so will have to wait and see