Say what you will about manufacturer's data, two glaringly bad examples stand out, and tend to support those who thing the real story of poor performance is being hidden:
1) the AB-130 Agusta web stuff is especially poor - no empty weights, and not even fuel volume, no payload range, no hover charts.
2) Similar stuff for the BA-609. No way to come close to a payload range chart, no hover data beyond the simple "HOGE altitude"