They did: HP's Elite x3. You can find bundles that include the Continuum dock for $299 at the Microsoft Store; looks like they're closing them out. They're enterprise oriented so the build quality is decent.

If you mean x86 compatible dockable smartphone, Intel cancelled plans for their x86 smartphone chip in early 2016 which put a stake in any hope MS had of doing that.

They basically priced it out of the range of those consumers that could benefit from it the most.

I always thought this too, but now chromebooks are so cheap it isn't really a benefit to have a dockable phone.