Suntour website points out that fakes are common.
www.srsuntour.com
Any silly prices are likely fake product, and uncertain performance. About £90 from a reputable bike shop, and will last years so not worth getting scammed to save a few quid.
Mid-drives and hills... the top torque sensor bikes like Shimano EP8 and Bosch Performance CX multiply rider input by 500% i.e. they put in four times as much effort as the rider in the highest assistance level. The rider is only doing 20% of the work, which is not a lot, but of course far more than the zero effort of ghost pedalling.
If you want to improve your fitness, there is no point having a cadence sensor bike.
All hills are climbable. You just need a low enough bottom gear to keep your cadence / pedal rpm at 60 or more at an effort you can sustain in highest assist level. Just don't expect to go everywhere at 15.5 mph, and don't expect the motor to work at 30rpm. Use the gears properly.
A 10 speed 11-42 cassette will do for most, I prefer 11 speed 11-51.