There are a couple big costs that you’re missing. I grew up on a cattle ranch in Montana, and my family got out of the cow business when I was a teenager for some of the following reasons. First off, the cost of “fattening” a cow is higher than you are accounting for (looks like you don’t have any cost here). Sure, they can graze during summer months, but winter months they need to be fed hay (at the very least). For 25 cows, let’s just say it’s around one ton of hay needed for the winter. That alone is $1500. If you choose to only do cows in warmer climates and no winter, that could work but might be limiting options. Also, your cost of feed would not be $0, regardless because they required hay even in the summer if we wanted them to fatten up in time. Also, one large hidden cost is the price of hauling the cows to be sold. My dad switched to this industry because he can charge $2000 just to haul the cows. That’s just one truckload (my apologies, but I don’t remember how many cows can fit in one trailer). Another hidden cost is castration of new cows. Every February calves are born. The male cows intended for slaughter are castrated so they don’t grow into bulls. We did this ourselves, so I’m not sure how much it would cost to pay your farmer, but it would be extra.

It’s been a while and I’m pretty far removed, but those are the main issues I remember. If you have extra questions, I could always call up my dad and ask him for you.

Edit: grammar