I purchased our first e-bike almost 20 years ago when most people didn't know they existed. It was a German made Esselte Meto with a 350 watt front hub motor at 36 volts. We loved it then and still do today.
The battery was literally 24 rechargeable D cell batteries soldered together. Had to replace the batteries twice and Batteries Plus had a spot welder to do the job. The electronics failed which I was able to fix but the nail in the coffin was the front motor clutch. Purchased a new 500 watt 36 volt front hub motor / rim / tire kit which included everything for about $150. Upgraded the old batteries with a single 36 volt 10ah lithium battery for $100 and the best anti-puncture tires I could find for $50 each and new seat for $25. The old bike has been back in action for years. It's better now than when we bought it. It was originally governed at 15 MPH, now 30 MPH. I've never run out of power but I peddle and normally only use the motor up hills or just having fun.
If you're doing the math that's $375. So whatever quality bike you get, add $375 and that's about what you should pay for the bike. Obviously, the reseller will want to upcharge for assembly so another hundred bucks would be reasonable.
Personally, I like a bike that looks, feels and peddles like a regular bike. In addition, I want it to be super quiet so I'm not noticed even when I pass someone on a walking path.
The motor, controller, cables, battery, etc will add about 35 pounds so starting off with a typical 30 pound steel frame bike and accessories is almost 70 pounds. You can trim some weight but normally reduces your motor's watt power, more expensive frame and hardware. 50 pounds is about as low as you will find and it can cost $3000.
Final note: It's about comfort and safety. Good brakes, tires, lights, seat, sitting position, quiet, odometer, bell, center stand, rack, and water bottle holder. Oh... by the way, it's not a girls bike it's a unisex bike. LOL
Attached is my other bike; a 2000 Kawasaki KLR 650. 340 pounds dry and will go over 300 miles on a single tank of gas.