They ARE heavier and costly, but like everything else you get what you pay for. But you can also do much more with them, simple as that, making their weight and expense more then worth it. You can still work your ass off, I do, I just go further and higher, then if I didn't have e power. You sound like you have never ridden one, give it a try, they are everything riding a regular bike is, but more.
My crane's e bike came in handy today, when the crew I was setting a Fiberglas swimming pool for found out they needed to do some more digging, and there would be at least an hour delay, I rode 3 miles to lunch, and then toured the neighborhood, in high 80 temps, "no sweat." Nothing I couldn't have done on a pedal bike, this was just more fun, faster, and I didn't need to sweat as much.
https://www.youtube.com/watch?v=LMMhTUvn93E&t=17s