Recently saw Lake MXZ 300 shoes on sale for $118. Pricepoint? One of the big Etailers. I bought mine a size too large. I wear thick wool socks over a silk liner. Good to 0 F. If you put on neoprene over booties they're good to -20F (-29C). For me anyway. You still have to get off and hoof it occasionally to warm up though.
one of the things I have been playing with is mounting my look clipless cleat over the rubber sole of my neoprene booties.. I do this with a pair of old Lake road shoes with a single strap.. I can still flip the booties down out of the way and tighten the strap.. This eliminates the need to cut a hole for the cleat and leaves the shoes instead inside the booties when you remove them. No hole in sole means no air leaking in.. rubber sole between the cleat/pedal and the plastic shoe sole slows the transference of cold to your foot.. I'm still playin around but these are working well.. and are very warm..
Initially I had cut down the inner boots from and old set of rollerblades to fit the shoes into before they went into the booties.. but these made the fit too tight .. and too tight killed the circulation.. the absolute final fix would be to invest in the heated inner soles... but that's an investment I'm not ready to shell out yet..
Strap on foot warmers
I use the Toe Gloze walker, to strap on over my shoes, for the mountain biking when I vacation in Colorado. Water resistant, with a velcro strap around my shoes, with a Heat Max warmer tucked inside. Work very well, and reasonably easy, even to peddle with. Never had them slip off, even on hard core use. Website is http://www.toegloze.com