To keep it simple and focused, yes, these people might otherwise have been in prison for longer than they actually were in prison, given that GPS is available to supervise them when they come out. If these people were not subjected to GPS, they might well be in prison for a longer period of time.
On the daily cost of imprisonment in England and Wales, I'm sorry, but I can't give you the daily cost. I need to do the sum; it's £35,000 to £40,000 per year, and no—