AB has to support those helpful distributors with mark-up and cover a fairly significant overhead and development cost. The Panelview plus is excellent hardware, and the direct tag access with the ControlLogix etc. lines is valuable. And, now that the early stage screw-ups are behind them, the software is powerful although not intuitive. A-B also has a high dollar marketing program.
Even with those considerations, though, the PanelView Plus is pricey. I suspect Allen Bradly can charge more because a great many people are willing to pay more. That logo gives many users a warm, fuzzy feeling. It is obviously worth it to those buyers to pay extra for the support and the comfort level and the quality either real or percieved.