depending on the breed and whether they are laying or meat birds 9 hens will eat roughly about £10-£20 worth of commercially milled food a month.
A 20/25Kg bag of food is around £10
If they are free ranging it will be less, if you feed wheat, maize, barley etc it will be less again.
Bedding costs... a large bale of wood shavings for nestboxes or floor litter will last a month or two and is about £7
Bale of straw around a fiver.
Worming treatments usually cost around £20 a time every few months or so.
Can be very cheap to do