Been out of this business for 2 1/2 years, but things don't seemed to have changed much other than the fact that more and more people seem to purchase from production sales rather than private treaty. I believe 90% of those get less and pay more, but that's discussion for another thread.
The most cows I ever owned was 18, and was pretty successful at keeping only 12 most of the time. I will have to qualify the rest of this by stating we had Exceptional Cows. All were high % Maine-Anjou for the first 11 years, and later retained 4 double registerd Simm/Maine heifers which began production in 2003.
Each year we picked the top 2 or 3 calves for our girls to show, and sold the rest private treaty for at least double the market price, and usually more. Each year we retired a heifer from the Show ring which we determined to be better than our weakest cow, we would sell that cow by private treaty for 2 - 3 times market value. We showed very few steers, so most Bull calves were sold as yearlings, also by private treaty. The only thing that ever went through the commercail sale ring was old, and/or barren cows.
I said all that to say this: in our 18 years of production show calves, 100% were sold as show calves, retained for breeding stock, or exhibited by us. Our girls and I did our fair share of word-of-mouth marketing, plus I put up a website about 10 years ago. Only once did I ever consign any calves to a sale, and I could have gotten more money by a private treaty deal.
So, I say, sure, you can easily sell 50% or more of your calves at a premium, but you better know your market, and have exceptionl cows which will produce a quality calf every time.