I suspect it's an attempt to replicate the Wall Street Journal model. The Wall Street Journal business/finance reporting, especially focused on the New York exchanges, is not generally replicated among mass-market newspapers. And it constitutes genuinely valuable work-related information to certain people who also have employer-provided expense accounts, these people go ahead and subscribe, and the subscriptions are paid by their employer as a business expense.
The Washington Post at least had (I don't know if they currently still do) a reputation for doing detailed nuts-and-bolts political/policy reporting on the US Federal Government in depth that nobody else matched. That is similarly genuinely valuable work-related information to certain people who also have employer-provided expense accounts, who will (presumably) then go ahead and subscribe, the subscriptions are paid by their employer as a business expense.
The Buffet-owned papers are, according to the article, going to go with "local, local, local stuff." Which is to say, the theory is the subscription will be worth it for the stuff that you can't get from a general-interest international paper. I'm more suspicious of this model; it doesn't have the advantage of the expense accounts. But it does at least try to sell something other than AP wire reports.