You might want to take a look at the Aventon Pace 500 or 350, definitely under $3k. They are pretty light but I don't know if they quite make it to 45 pounds. Just guessing, but my wife's Pace 350 seems like it's 10 pounds lighter than my Giant Explore E+3.
A couple of reasons why the Bushwick is under 50 pounds is that the battery is very small, and it doesn't have a rack, fenders, or lights. A 11ah (or larger) battery and accessories can add quite a few pounds.