I haven't done a systematic search yet. However, here's my impression. RJ's raise fares because of several possible reasons, 1) they take the place of larger jets resulting in higher load factors, 2) they take the place of more economical turboprops (My guess is that a Dash8-400 is cheaper to operate on a short segment than a EMB-145). When I book on a route served only by RJ's, it seems to be more expensive.