Here’s a theory: Hirst was the seller of “Girl with Balloon” and was in on the prank. Of course, the identity of the consigner is as shrouded in mystery as the buyer’s is. What is a matter of public record is that the seller acquired the picture directly from the artist, in 2006, the same year that Banksy agreed to participate in a show that Hirst curated of his art collection, at London’s Serpentine Gallery. Early last week, Hirst announced, through a spokeswoman, that he is scaling back his operation “to cut the corporate elements of the business.” Here’s hoping he has better luck than Banksy, whose stunt cutting fails to rise above the level of empty gesture.
Suppose Banksy's point is to comment on the absurdity of art celebrity, that "art" is more valuable because of who made it than anything inherent to the piece. That's not a wild assumption, given the stunt he did selling originals from a pop-up stand in Times Square.
Had this piece simply been sold, it wouldn't be in the news. Now we're not just talking about the high price and whether it makes sense, but the fact that literally destroying the work seems to be raising the value. I think that's making the comment loud and clear.
PS: I can't find a reference for Pratchett's definition of irony. Link?