It may be a myth, but in the UK record companies used to be said to bulk-buy (using teams of buyers in 'disguise'!) CDs at the stores which generated the music charts.Have you ever heard mention of publishers bulk-buying books to get a book onto the bestseller list? I wonder how much it would cost an author to try to inflate sales in this way. If somebody got a big advance - this is very hypothetical - of, say fifty grand, maybe spending ten or twenty grand on books would pump up sales enough to reach a bestseller list? So many people only look at the books which are on the bestseller list, this might then generate enough interest for some kind of a snowball-effect to occur?
Oh yes, it has happened indeed. More than one clever beast decided to skip the bothersome stuff of having actual readers buy the book and bought bulk copies himself. David Vise, author of The Bureau and The Mole did it in 2002. There's more about it here at The Book Babes
The Times list puts a dagger next to books that have "bulk buys" and has done so since 1995.
Like everything there's a way to manipulate best seller lists. You've got to be seriously self involved to think buying your own way onto the list means much. Like stealing Miss America's crown so you can "be" Miss America.