Feck buying them for ferrets at the price they are in shops. I've recently got a snake again and i've set up two tanks of mice and one of rats, what I don't use myself will be either used by mates or sold to pet shops but theres no way i'd bother giving mice to a ferret. An adult frozen mouse is going to cost roughly a pound from a pet shop and if you have a hob who could eat say 5 a day thats a pretty expensive diet even compared to James Wellberobbed.
Shoot/catch woodies, squirrels or rabbits or ask at chicken farms for any culls (not day olds, the meatier older ones), theres always someth