I have noticed this already a long time ago, but as Gold. When logged in through the A-club site (or when I have added my A-club number to accorhotels.com). The first rate shown is often more expensive than when I search "anonymously".

Generally the cheaper rates are available somewhere down the list, or by changing the room type.

With one of the other main hotel groups I would probably complain to them about trying to rip off their most loyal customers. But since I have basically given up on making sense of Accor, I just ignore it...