I do much better selling them just past weaning. Like to have them at about 200-225 pounds, and I have regular buyers fighting over mine! I demand top dollar, but sell top quality, and people pay.
I have a flat rate purchase price set up with the dairy, and take all their bull calves. $80 each, all year, no matter what the market does. Milk replacer is pricey, I pay over dollar a pound, but have a "technique" for weaning. My average this year is weaned in 39 days. Saves a bunch of $$$.
Problem is you really got to be on top of your game. People that just throw milk and hope for the best ain't gonna break even. Too many things can go wrong, you lose one and your profits are in the toilet.
And there's a lot more to weaning and just "toss them on grass", like so many "hobbyists" do out here.
Your never gonna "get rich", but you can turn a fair profit, for an awful lot of labor!!