I have never bought from Murry McMurry, but my aunt, who has shown poultry for decades and is very serious about it, will only buy from them if she can't get a breed from a quality breeder. I'm sure she still has to cull some.
A more current example of helping Sand Hill - I obtained a line of Coturnix quail that lay bright blue eggs. I sent a batch of eggs to Glen and intend to send some half grown birds soon. Also, I just won an auction for Spitzhauben chicks from Greenfire Farms. They are different colors than what Sand Hill sells, but hopefully will have good type and be useful for an outcross to his line. First, I have to grow them out and see if I can produce chicks next spring. Then, I suspect
@feliciadawn will want some of the first one I manage to hatch (assuming her little one really is a roo after all.). After that, I can send some chicks to Glen. Like me, he is fine with getting chicks a bit later in the year, spring is so busy with people wanting to buy chicks, that it helps to get most of my own breeders from the summer hatches.