It has driven the price up, I think.The result is the same. In fact, no one other than the author could prohibit the sell of a book. So it is even a broader ban than a government or some other entity "banning" the book. Whether its terrorists, hackers, or mentally ill people like the Columbine shooters taking issue or being influenced by a work, you can't simply allow those types to dictate who reads a book or sees a movie. I think King's intentions are good but misguided. It certainly is his legal right as the author not to have it in print. That's not the issue though.
A 1st edition, first printing hardcover of the Bachman Books goes for 200 bucks now!
The Bachman Books: Four Early Novels: Rage; The Long Walk; Roadwork; The Running Man ---with a New Introduction By Stephen King " Why I was Bachman " by King, Stephen Writing as Richard Bachman: N.Y.: NAL / New American Library (collects the SIGNET paperback editions), 1985, 1st Edition, 1st Printing 9780453005074 Hard Cover, First Edition - Leonard Shoup (Member of IOBA)
If the link does not come up (possibly too long?) just go to abebooks and look it up.