When you buy a cow, you are (hopefully) buying two things: the calf she is going to produce and the cow herself when you eventually sell her. Those are the only two ways she puts money back in your pocket.
Net Proceeds is what you collect when that calf sells at weaning after the sale barn takes their cut. We use Salvage Value for the cow herself, based on her weight and today's cull price per pound. This is conservative on purpose. It represents the floor of what she is worth to you if everything else goes sideways.
Between now and the day that calf sells, you have to feed her. That total bill is the Carry Cost. It is the price of time.
The math: take the calf net proceeds plus her salvage value, then subtract carry cost. That number is her NPV (Net Present Value). It is not a prediction of what she will make you. It is simply what she is worth today, based on today's prices and your costs. Not yesterday, not six months from now. Right now. It lets you see her relative value so you can make a more informed decision at the point of sale.
Compare that number to the asking price. If the asking price is lower, the market is giving you a discount. If it is higher, you are paying a premium. That does not necessarily mean walk away, but you should know when you are paying above fundamentals and have a reason for it.
For pairs, the same logic applies, but the calf is already on the ground. Instead of waiting through gestation, you are only carrying the cow from the calf's current weight to weaning weight. The calf weight segment you select determines how many days of gain remain and therefore how much carry cost sits between you and the paycheck.
This tool models one production cycle. A full herd valuation accounts for multiple calving years, replacement timing, genetic merit, and other factors that compound over the life of the cow.