how much do chickens cost /best ones for most eggs

[Bjm]

My teenage son has an incubator and kept asking for some chicken eggs, i managed to put this off for nearly two weeks thinking that
we had enough hens and he would stop asking and move on to something else. so while i was on my travels i bought half a dozen free range eggs from a local farm for him to incubate expecting that nothing would come of it, but to my surprise five hatched.
so if you can incubate them you can get them very cheap. (just check that that there is a cock in with the free range hens)