I have about 200 miles on this
Co-Op Cycles (REI brand) e-bike which I purchased a few weeks ago, and have found it more than adequate for ALL of my uses (including hauling my 40 lb herding dog in her 30 lb bike trailer)—especially at this price point I don't think there's a better value out there. Definitely one to consider! The rack is integral to the frame, and total capacity/limit is 300 lbs (including rider, all gear, etc.)
I do not know what the cost of spare battery packs are, but they are easy to swap in and out. I get about 30 miles per charge on high-assist mode, have actually never run out of charge on lower modes so not sure how long it takes, as I generally top it up at some point.
EDIT: That 30 mile range includes dog-in-tow!
EDIT 2: Ah wow, I wish I'd known about the RadPower bikes, they look like amazing machines and I probably would have gone that way, judging from the specs on some. Shucks.
