I've had two of these (700s) back in the day -- a sedan and a coupe sport (my first CS!). Coupe was a daily driver for us in grad school. Accelerator linkage stuck wide open on my wife one day and she galded the roller crank before she could shut it down. Unfortunately, very few of these engine parts come from the motorcycle 2-cylinders, so repair is tricky. I unloaded both of them, plus a trailer, at a classic car auction for $900 in 1978. Nobody knew what they were. Another of my prescient "investments."
By the way, these are basically tin cans and would get flattened in a crash. That, plus repair challenges and rust, is probably why so few remain. They were basically disposable. In this case, rarity does not equate to desirability. Then again, I never dreamed I'd see an Isetta sell for $35K.
Don