First of, B&H is only one of million places where you can buy Canon lenses.
Secondly, show me one pancake large aperture prime for mirrorless which is sharp wide open across the frame, which isn't priced over 500$. There is only one, which is the 22mm pancake.
The equivalent Sony lenses are all inferior. The 20mm F2.8 is a joke compared to the Canon. Samsung is pretty good though, but the bodies are not that great in terms of handling, and last time I checked (which is a while ago) Jpeg output of Samsung was terrible.
And no, I know there is much more out there than EF-M, but that is beyond the topic isn't it??
Last time I checked I was in the Canon EOS M talk forum...