The closing round, defined
A best and final offer is a final submission requested from the remaining bidders in a procurement or deal process, covering price and any last commercial terms, after evaluation has narrowed the field. In principle it lets competitive tension do one final round of work while the buyer still has alternatives at the table.
What it does to behaviour over time
Used once and sparingly, a BAFO extracts real movement. Used habitually, it changes what first offers are: a market that knows your "final round" always comes learns to hold margin back for it, so opening bids arrive padded and the BAFO merely claws the padding back. The hollow version is worse: a BAFO issued when the decision is already made teaches losing bidders that your processes cost money and return nothing, and the strongest firms remember at your next tender. There is also an information cost inside the round itself. A vendor squeezed to an unsustainable number does not donate the difference; it reappears as thinner staffing, the B-team or change orders.