OTOH with an electric motor you might not need gearing at all - the motor will help you in a difficult situation: https://www.theverge.com/2020/7/28/21344679/gogoro-eeyo-1s-e...
I don't know if part of the reason they are so expensive is because they are a niche bike item, and bike stuff is already hideously overpriced, or if there is another reason.
I also am not certain on the exact reasons why internal gear hubs and belt drives are more expensive. I imagine manufacturing those hubs are more costly just by the nature of their design. It also used to be the case that you needed a specific frame built for a belt drive to run one, but they make breakable belts now so that's no longer a huge restriction.
I have heard in Europe where bike commuting is far more common in the US where I'm living that belt drive and internal gearing are more common, but this was hearsay.