i cant believe nobody sed this one yet but the most desired and valuable bike are Rupp Roadsters, Roadster 2's and Black Widdows. they go for well over 1000$ restored and the roadsters were street legal from the factory. (not shure about the black widdow) some people even make a living at selling parts for them. (black widdow mororsports for example.) also in my opinion they are some of the best looking mini bikes ever made.
Well those are classified as minicycles actually and are rare and desirable to many but not as rare as you think. We have plenty of Rupp fans here even many Rupp minibikes classified as minibikes by wheel size are not that rare and desirable minibike by any stretch of the imagination but there are a couple of exceptions that bring good $ still.
Now your Savage, Go-Kart Cycles, Greenhorn Enduros, Flexos, Capers etc are truly rare. Hell the Micro Cycle made in Tulsa Oklahoma is ultra rare, I've seen two and I live in OKC and have run an ad here and Tulsa CL searching for one for years with no luck when I had a grand to blow and now I just have the $ ready for one to pop up but I wont hold my breath.
However Rupp Dart Cycles are as or more rare than Black Widows and some of the above mentioned rare minis by a long shot if you want to talk Rupps. The Dart Cycle is on many of our bucket lists including mine, I ain't holdin' my breath on that one either.:laugh: