Where would you buy it? Unlike fish where the prep is done in front of you, a cow has to be prepped before you even see it, very soon after it dies (or it will explode). And it weights 400 kg.

Or maybe you want to buy it when it's still alive? At least you can walk it back to your place. But good luck dealing with the killing and the blood.

Sometimes you can buy whole parts of game (a leg or a shoulder maybe) but that's about it! ;-)

We call up the rancher / farmer and buy the whole cow then a custom slaughter house / butcher get it and cuts it up. You probably want it hung for 30 days in cold storage. People do this, a co-worker goes out to Montana each year. Some grocery stores in the area do this, it's cheaper than buying the individual pieces.

You can buy a cow and have someone kill it and butcher it. I've known people that have done this.