> I think the problem is range, you won't be able to hide much battery, the one on my bike weighs 6LBs and is quite bulky.

Interesting, that seems to be exactly what I was thinking of. The good thing is, it seems you could use it without a battery, or with differently sized batteries depending on need. If I'm reading this right, the motor, wiring, etc, weighs about 1000g, then a 6Ah battery another 850g, or a 9Ah battery 1250g. So only an extra kilo if you just wanted to use it as a normal bike, and if you're commuting, you might know exactly what capacity you need, and could just take that. Especially in cities, there's a lot of carrying bikes up and down stairs.

Just needs to be a lot cheaper than 3000 Euros!

Can you pedal and use the motor at the same time in a regular ebike? I think what the parent posters want to be able to turn off the motor completely.

You can; it's called "pedal assist", and usually, the motor controllers can be set to do it at different levels of pedaling intensity. It's usually implemented by spacing magnets around the crankset and then calculating how fast they're passing by a sensor.