I bow to your superior knowledge

As I said , I do not have any personal knowledge ,only what I read .
As Ken Clarke said recently
Sentencing should not be based on cost, but on principles of retribution, reflection of public anger and the effective prevention of further crime. It costs more to put someone in prison for a year than it does to send a boy to Eton – on average £38,000. The taxpayer is providing keep and accommodation – albeit in grossly overcrowded conditions – at expensive hotel prices for 85,000 people.