Puslishers colluding on a single point of sale they and only they control would be a pretty serious anti-trust violation in the US (where all these major publishers are located). And rather obviously so. I doubt they'd be that stupid.
Plus, as has been noted, there are already authors making scads of money by selling through Amazon direct for .99 a copy. And it only takes one rogue publisher, still selling through reputable web sites like Amazon or Barnes & Noble, to break the cartel anyway.
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