Buying an eBike is a lot about choosing the motor you want then hunting down a bike that uses the motor. I would strongly suggest that you buy from your local bike shop and buy the brand that the bike shop normally stocks.
Cost me £1700 (about €2000). High-end Mid-drive motors pushing 75nm+ are expensive. Bosch Pro CX line and Shimano Steps are the other two types available. If you start looking around, you see the cheaper mid-drive, i.e. Bosch Active Line starting around £2000 and are suitable for lighter people. The high end motors are usually combined with high end parts and bigger batteries. Thus you end up with bikes costing between 3-4k.
It's saved me an absolute fortune. In fact after owning it for a month, my wife wrote off my car. We just took the insurance money and didn't buy another car going down to a one car family.
Electric bikes are not as easy to take apart and sell on. (I'm sure I'll be proved wrong.)
I have a gold standard D-Lock that is side mounted on the frame (weight not an issue) that I use when parking up. There is also a dutch style rear wheel lock mounted to the frame I also use. The battery has a key that keeps it locked to the frame. The head unit for the eBike display is removable and I take that with me whenever I leave it locked up making the motor unusable.
Basically you're trying to steal a 25kg (55lb) bike with multiple security features and relatively unique electric parts that people would be wary of buying due to lack of guarantees.
Sometimes if I'm popping into a shop/café, I use the bike stand, lock using the dutch lock, and just take the head unit off. I'm guessing somebody could pull up in a van and just lift the bike but the opportunistic 'snatch' is so not going to get very far.
I'd recommend multiple bikes. Ebikes can be inherently boring to go for a long ride on as you are essentially free-wheeling. Nothing quite like the quiet of the road as you are cycling along. Ebikes always make a whirring noise.
As a way to get from A to B quickly, nothing beats them in a city.
I did an Air Pollution piece for the BBC comparing exposure of somebody walking, cycling, and driving in and around Bath. As the cyclist, they told me I was travelling around the city a bit too fast for the pollution monitor to get all my data correctly. ;)
I don't have an e-bike, but a friend got one. In addition to the motor, his advice was that you should choose the control system. There's a small handful of companies that make the controls, and his impression was that he preferred the behavior of one particular brand over the others.
I'd still go with whatever your local bike shop stocks. They do go wrong at some point and you will need a repair and even a courtesy bike while it gets repaired. Shipping a bike is not fun.
I daily a Felt Nine E-20, it's a mountain bike with front suspension. I also have a Cube 400 and a Juiced u500 cargo bike.
I recommend spending $3k on a bike with a Yamaha or Bosch motor, it's easy to justify that crazy price if you look at the money you'll save in gas/payments/gym expenses. Most importantly, I enjoy my commute now and I feel like a part of the city in a way that car commuting doesn't give you. Also, get a pedal-assist bike not one with a hand throttle, trust me it's not better to have a throttle.
Disclaimer: My new startup is ebike related but I'm not going to be selling any bikes or hardware.
You can choose how much help you want from the motor and you normally go faster with a ebike (using a bit less muscle power).
I shaved a few kilos off my weight by using an ebike for a few months.
If you like your bike commute and don't mind getting sweaty you might prefer a normal bike.
No, I still expend enough power to keep my heart rate at ~160bpm during my ride, but now I cut my commute time in half and I ride more than twice as often.
My pick was the Brose mid-drive motor available in Tour 50nm/City 75nm/MTB 90nm models. I then bought an ex-demo one off model from a localish bike shop. https://www.ebike-manufaktur.com/en/e-bikes/11lf-shimano-deo...
Problem with battery meant it took 11 weeks to get it back on the road as the shop did not have a relationship with the bike manufacturer.
The bike however is phenomenal. I weigh 130kg and it takes me up ANY hill in Bath. There's a couple of 1 in 3s that I can cycle up one handed.