Simple electric bikes (new) range around 1K-3K for the ones looking more like a bicycle and around 2K-4K for the ones looking like a scooter.
No registration and insurance is needed.
Prices are right. Registration is needed (in Beijing at least). Insurance is something you should look at in more details, can be very case specific.
Not needed for Chinese citizens as those are considered as bikes and thus covered by your civil liability insurance or however that thing is called in english, just the same insurance as if you were riding a bike.
But if that insurance in your case is provided by a foreign insurance company, then they probably consider those as motorized vehicles and won't cover anything for you while using these.
I mean it's not required to have an insurance to drive those, but if some trouble happens, then you will have to take care of this on your own. Just don't send anyone to the hospital by riding it!