We've been raising Longhorns for 12 years; butchered our own for past 11 years. All our LH's are grass fed, no supplements (except mineral & salt), no cubes, no bagged feed.
The ones we slaughter for steaks & roasts are under 24 months old and in the 700 to 800 lb range (steers, cows, heifers, or young bulls). Compared to "store" beef, we calculate one of the animals gives us about 250 lbs of packaged meat with a "store value" of around $1200 to $1500 (for our own consumption). Any older animals that no longer are breeding, etc., are turned into hamburger or summer sausage.
We slaughter one each year for the 2 of us...we eat a lot of beef. We also have processed (between 6 and 9 animals) at a USDA inspected facility and sell packaged beef at several Farmer's Markets. One animal can generate around $2,000 to $2,500 in beef sales (ranging with hamburger at $6.00 lb to tenderloin at $19.00 a lb.). Selling summer sausage at $10 to $12 a pound. Many repeat customers. The "sale barn" check for these animals would only be about $500 each...been there, done that. Note: slaughtered ones are those that are not suitable for registered breeders and/or those not wanted for our own breeding (replacement) program.
In a nutshell, yes, it is cost effective for us and we do make money on our USDA processed packaged beef sales with our lower inputs in our grass fed program.