It has little to do with the price being set by a computer or a person. He sees the price for everyone else is one third cheaper. He doesn't say it, but without making the connection to the price fixing anti-trust action, a reasonable conclusion would be that since the book is one in a series, and Amazon knows he bought the previous book, it has jacked the price for him since he's already "hooked." That to most people would be a questionable pricing strategy.
The anti trust action makes more sense, but he probably didn't make that connection.
If you go to a flea market, and the lady at the stall gives the person after you a 20% lower price because you looked rich (inelastic) and they looked poor (elastic), would you be angry about that?
The anti trust action makes more sense, but he probably didn't make that connection.