Earlier quoted context omitted.
This bike booster will probably come in at less than half the cost but the Bimotal kit is another option that doesn't have the tire wear issue, offers better performance, and the form factor is much nicer. https://bimotal.com/products/elevate
Wow, $2k? You could get a decent ebike for that money. And the installation doesn't look any easier than a hub motor... Only seems worth it if you already have an extremely nice bike. I think of friction drives as being aimed at budget-conscious commuters, not serious mountain bikers.
That being said, having driven electric bikes for a while, here in France they're ridiculously limited in speed and power. 25km/h limit on flat land usually makes sense (except on long straight lines), but when you get climbing even slightly you get down to ~10km/h and have to provide more effort. I guess that's where the 750/1250W 70Nm unrestrained motor comes in handy, and if you live in a place with lots of small hills the choice is either that kind of motor or a car, not the 1000€-total Decathlon/Carrefour electric bike.