Never been but seem like a good rule if they do, although are you not prisoners to their hugely inflated costs once you get there until your release date?
Yes - if you choose to buy stuff
I seem to remember the pubs are about normal prices - food and drink
shops are small and expensive but as you can take your own food and stuff then it is your choice
pool and slides etc always used to be free
Bike hire is not cheap but your can always take your own
They do try to give the impression that you are stuck on site - but you are not really - you can always go back to the car park and take the car out to get some cheaper shopping - although it would be a a walk if you are at the far end of the park