Why would you only get 7 calves out of a cow? Most of our older cows are between 12 and 15 years old before we even concider sendin em to town.(there are the odd ones that get culled for a bad bag at 10 or 12 but not many) As long as they have a calf and can raise it right, they get to stay.
We only held back 13 heifers last year for replacements. I can guarantee you it won't cost us $1300 a piece to get em to the breeding age. Between hay, mineral, and vaccines it usually costs us about $200 per cow per year. Averages out to about the same for replacement heifers. Even tho they don't eat as much hay that first year as they do the second year. If you have the ground to raise em, I can't see where anyone would wanna go out and buy replacements, unless you were just tryin to improve your genetics with some new stock. But I"m a believer that choosin your bulls for your improvements is much more economical.
We had this discussion a long time ago on another board, I was criticized real bad for claiming that our expenses on our cows was impossible. It is possible...when you don't have any notes on new equipment....no land notes, no notes on your cows.....etc bale your own hay. When expenses are at a minimum it's very doable.