[ammojamo]

All good points, but I would add a couple of things:

1. Scale also comes into play: We only have 8 hens, and are able to significantly supplement their feed with scraps from the kitchen, which are effectively free. The chooks are free ranging over a similar area (~half an acre), so the lower density means more free-range food for them, I guess. As a result, our feed costs per egg are actually much lower than if we had more chooks, and keeping a few old hens around is a negligible cost for us.

2. We regard our chooks somewhere halfway between pets and livestock - it's not a binary choice. We enjoy having them around so they have some intrinsic value for us, but at the same time if they were getting too expensive to keep, we'd be OK with occasionally cooking one up.