Part of the issue is that none of the publishers were willing to individually bear the the costs of not selling through Amazon. They were only willing to threat

Part of the issue is that none of the publishers were willing to individually bear the the costs of not selling through Amazon. They were only willing to threaten that together. To continue the analogy: If, for instance, the Top 100 paid app authors of Android apps banded together to force Amazon and Google to change their terms by threatening to take away their titles that would certainly raise at least a few antitrust eyebrows.