[SixSigma]

Why not just buy an eBike, there's a few under $1500 in this best of, and one sub $500

http://electricbikereview.com/top-10-electric-bikes/

[hengheng]

Decent road bikes (the one that you use more than 10k miles per year) are more than $2000 on their own. The electrical components go on top of that.

[mikeyouse]

Yeah, the $3,500 ones are super-lightweight with hidden components. If you don't try to conceal the functionality of your e-bike, there are plenty at much lower price points.