The only difference is that once they hit a certain weight, they are not gaining $1.75 worth of lbs, they are gaining 1.40 worth of lbs.... You have to sit and decide where the "equal return" is... For us here, anything over 600 lbs is going to drop off in price per lb and puts more demand on the grass/soil. We can run a few more cows, sell a few more calves, and then actually make the grass last longer to feed those cows because once they are not lactating, they are demanding less out of the pasture they are on and are actually gaining weight themselves so are in better condition to calve and produce milk for the next calf.
Years ago I did a chart on lbs of calf compared to price received... cannot find it but I am going to do another... did it on graph paper that showed where you were getting back the same money for xx wt calf at yy price .... maybe someone with more computer expertise could replicate something like that... It was to show a neighbor that he was maybe getting more per calf in xx dollars, but he had less # of head to sell since they required more land/grass to get to that point and his check was nearly identical to ours total.....
The guy we used to help and who passed away, used to wean his calves off his cows and then pour the feed to them for 60-90 days, then sell them... He always topped the sale and was the kind that liked the bragging rights. My son did some comparisons and after you took out just the feed costs, not counting the time and effort to feed them, that we were getting nearly the same for our calves in GROSS returns without all the inputs and leaving them on the cows up to selling. Because the feed was high and ours were still on grass and their momma's. Now we do pull/wean because we are also buying calves to make up bigger and uniform groups... but the silage is still cheaper even with the grain topdress..... than he was feeding just the grain... if we weren't buying cattle to put together groups of stocker calves, working cheaper bull calves into steers etc.... it would be questionable if it is worth the cost plus the time to do so.