Lets say a high egg production breed lays 1000 eggs in her lifetime.
Lets say she has an average lifespan of 4 years.
6 eggs here in the UK costs around £1.50. This works out at £0.25 per egg.
1000 eggs comes to £250.00 worth of eggs in the hens lifetime.
A high production breed needs 100 grams of feed per day. Over 4 years this amounts to:
365 days x 100 grams = 36500 grams for one year.
4 years x 36500 = 146000 grams over her lifespan.
A 20 kg bag of feed (20000 grams) costs on average £20.00 in the UK taking into account delivery etc.
Feed works out at £1.00 per kilo on the price above.
0.10 per 100 grams.
100 grams at £0.10 x 365 days = £36.50 per year.
4 years = £146.00.
This leaves you with roughly £100.00 for coop, waterer feeders, feed trays, maintenance, health treatment at it’s most basic (mites, lice etc) in order to make a profit.
I don’t know what the average backyard coop costs but I’ve seen coops from a few hundred pounds to a few thousand.
I think for most fully confined backyard chicken keepers the hopeful “we feed them and they feed us” is in reality more like, we feed them and get some really expensive eggs for our troubles.