I bought my current bike from Walmart for about $150, and would be interested in updating to an ebike if they were in the $500 range.
Also, there are folks who expect a flood of used bikes to hit the market. As with conventional bikes, the pricing of cheap bikes is affected by the pricing and availability of used bikes. A new bike has to be priced cheaper than repairing an old one.
Actually just bought this one. It's obviously made to a price, but quite rideable and has gotten me out riding again and a little more excited to exercise.
Edit* full disclosure: I owned one of these and returned it because I decided I wanted something a bit more high performance, but only because I lucked into a free Bosch battery pack.
In fact, that's the best way to do it. Get a good bike and modify it into an electric. You get much better customization and quality for the price.
But that's not for everyone. Perhaps someone with access to funding can start a chain of conversion shops... but honestly, Swapfiets is cheaper.