In my tiny little photo corner of the world, it is really difficult to say no when somebody wants the equivalent of a 4.5x3 foot print from one of my 35mm negatives. I don't sell much work, especially recently, but was approached by somebody who wanted a print from one 35mm negative as three vertical pieces, each 1.5 x 3 feet, where all three sections together work out to be 60x36" panel, with the same crop as my original 18x12" print, except for the 3inch space between each section... I ended up telling him no, even though it was a good opportunity. Perhaps I should have sold it that way, to make some money back from this vocation, but silly me thought my integrity was more important. I'll probably regret it.
I can understand why McCurry wouldn't mind selling a 60x40 print. As long as he gets paid for it and he doesn't mind having his pictures exist in that size, good for him!