The two numbers are real because they're set by two completely different groups of buyers. The bulk price is what someone will pay to take the whole 100 acres in one transaction. Very few buyers can write that check, and the ones who can are investors who need the price low enough to make their own work worth doing. The retail price is what one household or one small farmer pays for the single piece they actually want. That group is enormous by comparison, they usually only need a fraction of the money, and a 5 acre lot with its own legal description and its own deed is something a small local bank or a seller-financing arrangement can handle.
So the spread isn't magic. It's the price of turning something only a handful of buyers can absorb into something hundreds of buyers can absorb.
As for why the original owner doesn't do it himself, some do. The ones who don't usually lack one of the three things the process needs, which is money up front, patience, or familiarity with the county's rules. Splitting land costs real cash before a single lot sells, and it can take a year or more with no guarantee the county says yes.
One thing that trips people up reading decks like that one: the gross retail number is not profit. Out of that $9,000 an acre comes the survey, the engineering, the plat filing, whatever access the county requires, property taxes for every year you hold, and the commission on each individual lot sale. Ask the sponsor what the net is per lot after all of that, and how many years they assume it takes to sell the last one.
