I do not understand the mathematics behind the dilemma. I'm assuming only the firts chicks cost money, because down the line they will breed.
But feeding them, housing them - vitamins and doctoring costs a lot of money.
So anyone with couple or more chickens - how much does it cost to have them on the table? And realistically how many eggs do you get?
It's worth noting that their ability to avoid predators depends heavily on the predators where you live.
Coyotes and bobcats decimated my chickens regularly when I had them. They'd tear right through chicken wire in the winter time. I'm also not unconvinced that a few of the smaller adults didn't die to some of the larger hawks in my area, but I have no evidence to back that up.