84,000 pays $250 per folio side. People pay, are getting paid, etc. Nothing is free. In this case, since the main donor for this project is a millionaire several times over, it is no sweat of his or her back since most of those millions were donations anyway, to begin with. Someone always pays. The metaphysics we attach to this or that economic exchange is not the measure of whether someone paid something or not.
If you try to buy books from the BDK, you have to pay for them. If you want to download the PDF, well, that is "free."
Thus far, 84000 has avoided printing its books. If they were to print them, it is like that they would have to charge for them. Nothing is free. Someone always pays.