As a co ordinator for Hen Rehomers UK, we do stress before people take on the hens, that if they are wanting them for lots of eggs, then do not take on ex battery hens. Most of the people just want a couple for their garden, which is fair enough, pet hens who may lay eggs, which will suit these people.
Having said that, I have a lot of ex battery hens in my flock, who have laid very well. We do try to discourage people who want them for a business, or to sell the eggs. This is for fear they will get them, find they are not laying well enough, and then either sell them on, or eat them.
I have noticed that hens in general do seem to be very expensive. POL near us start at around £8, but have seen some for £10-15 as well.
I suppose the breeders have kept them for all those weeks, and fed them, so that is what it cost to rear them.