Earlier quoted context omitted.
I don't follow. The price-fixing claim stems from publishers forcing Amazon to raise their prices by threatening to cut off Amazon's access to their books; it doesn't have to do with competition from the iBook Store. However, it alleges that Apple was complicit in forcing Amazon to raise prices, not through competition, but through threats.
Apple offered a better deal. That may be a competitive threat, but that is competition, not a threat of... violence? criminality? What are you implying? Amazon was not forced to do anything, they chose to offer the same deal Apple does because they wanted to keep the business. If Amazon only capitulated to this deal in order to keep the big six on board, why do they offer it to everybody, including small publishers?…
The incentive that Apple offered was helping publishers control downstream prices, which is exactly the price-fixing this case is about.