I absolutely love my Rotrax. This probably won’t help establish a market value on a frame 30 years newer, but I paid $600 locally for the entire bike. It’s an all chrome Super Course from 1953. Rotrax has been around for many years and has made some stunning bikes. Here are a couple of shots from the day I found it. Seller originally tried to get $1000 for it but there were no takers. Rotrax bikes can be quite special.
It looks to me like the subject frame is very well made and beautifully finished but $800 is quite a bit for a starting point.