Aren't most beef cattle (livestock in general) sold by weight? Run it across a scale and the price is per pound on the hoof. Here's a report from Greely, CO in June of this year: https://www.ams.usda.gov/mnreports/gl_ls134.txt Greeley, CO Mon Jun 25, 2018 USDA-CO Dept of Ag Market News
The prices quoted are in hundred weight, so a price of $83.50 equates to $8.35/pound... $83.50/100#
ETA: As pointed out below, the decimal above is misplaced it's 83.5 cents per pound, not $8.35
Are you selling it as "old veal" or baby beef? At 8 months old a holstein will have very little actual meat on it. Unlike a beef breed, dairy breed animals will grow more frame than actual meat(muscle) for the first year. A beef breed will put on an almost equal amount of meat along with the growth. Just the way they are designed by nature. If you are doing veal, then as much milk as it will drink for about 4-5 months, with limited grain, and hay. The meat will be very pale pink ( I do not believe in white veal as the animal is anemic) But at 8 months you are talking an animal that will weigh in the 4-500 lb range if it is eating and growing good.
The best way to do it is to see what they are bringing live weight at the area livestock market. Example. Here right now prices for holstein dairy steers is in the $.50 to $.65 a lb. It is not worth the milk replacer to raise them. A 3 day old holstein bull calf was bringing $75 to $150 a month ago. Right now you are looking at $40 to $75 a head. So if I wanted some holstein steers to run out I would go buy 600 lb ones to put on grass for less than $400 a head and not have the hassles of bottle calves.
All that said is not to discourage you. Just after 40 plus years of bottle calves, nurse cows raising multiple calves, etc and so on, I am only trying to help you to realize that you will barely get back what money you have in it not counting your labor....which is always "free".
So to price. Say $.50 lb for round figures for live weight. That's $400 for an 800 lb animal. Age means not too much as they all grow differently. You will not ordinarily get a holstein to 800 lbs at 8 months; probably not until 14 months. They breed holstein heifers at the 800 lb size at 14-16 months to hopefully calve at 1100 lbs at 24 months. If you are selling it by the hanging weight, then double the live weight price; because you are going to lose at least 50% of the weight on a dairy animal. ESPECIALLY one at 8 months or so as they are nowhere near to being finished. A holstein that is fed out to a finish weight will weigh at least 1,000 to more often 1200 lbs, or more. They have to grow frame to put on meat.
This is not saying you are doing anything wrong. IT IS THE NATURE OF THE BREED. An 8 month old angus steer will weigh in the 5-700 lb range and be rounded out. Not "finished beef" but very edible as baby beef. An 8 month old holstein will hit 4-500 lbs if it is getting real good nutrition and plenty of it. They eat like hogs as they are growing. They are growing frame and bone.
I've raised alot of jersey and jersey cross calves as steers for meat. Try to get them to finish at about 25-28 months. They are worth less than holsteins; $.40-.60 lb. live weight right now. They have less bone density as their bones are a bit smaller and thinner. A little more meat at smaller sizes. Most of mine will weigh in the 900 to 1100 lb range at 2 + years. Hanging weight will be about 60% at that time and actual edible meat about 1/2 of that.. I figure 25% of the live weight will be actual meat in my freezer. It is usually always a little more than that, but it's a good figure to start with. Beef animals will vary due to fat, but will run a little better than 35% of live weight, actual meat in the freezer.
By the way, . Hope that this helps a little. I probably got into too much but so many people have expectations that are just not "real life". I have eaten my own beef for over 40 years, do not buy any at the store.
I also buy bottle calves/dairy cow calves from local dairy farms and raise them to sell. I never sell by weight because it's not worth it where we are from for a cow like that. Honestly, an 8 month old Holstein bull calf id give you $80-$200 for it depending on the season. I don't even think id pay a penny more if you raised it another year. Sad but true. Where we are it would make more sense to sell it as beef.
I actually found a ton of dairies that breed their Holsteins to Black Angus bulls. I buy the solid black ones and I sell them. I get the same price for them as I would any other Black angus that comes from our farm. I also now have been buying the heifers, bottle raising them, getting them pregnant and selling them. Because they are so friendly and such good mothers people offer bigger numbers for them. $3,000 bred is the last offer.
Apples to oranges tho. You're looking at it from a live animal perspective and she's asking about it from a meat perspective.
What they're worth live and what they're worth cut & wrapped are 2 completely different things.