The way I see it, the lighter weight calves DO bring more per pound. BUT, if you pencil it out, that does NOT = more dollars.
Just looked at the local market reports, and granted, they ARE yearling sales, but here you go.
4-500 weight steers 1.25-1.30
6-700 weight steers 1.10 - 1.25
So take a 450 weight at 1.27 = $571.50
And a 650 weight at 1.18 = $767.00
120, 450 weight calves would net $68,520
100, 650 weight calves would net $76,700
That is $8180 more $ for the heavier calves.
Even if you used 600 weight calves @ 1.20 = $72,000 you would make $3480 more on the heavier calves.....
And, if you figure on feeding 3% of the cows body weight, you would feed 6# more to a 1200# cow than to a 1000# cow. If feed costs 2.5 cents/lb, it works out to 54.30 more per year per cow = $5430 for 100 cows per 360 days. Costs pretty much the same to feed an extra 20 cows for 360 days. 20 cows x 30 lbs x $.025 x 360 days.= $5400
But then you need to figure in the expenses like vaccination, worming, any treatments, and death loss you would encounter with 20 more cows. So however I figure it, I would be making MORE money with fewer 1200# cows than more 1000# cows.