I broke down and bought 45 North FasterKatts several years ago. I had several systems of produce bags and socks. at time shoe covers and other times neoprene booties but the FasterKatts are simpler, easier to put on and take off (for that agimg man's run to the rest room upon arrival), walk better at the farmers market and don't rub and wear out my cranks.
Yes, $200. And they are only rated 25F. (On this skinny, always cold guy, they are actually fine if not truly warm for 3-4 hours in 25F. (Portland, OR. That covers the vast majority of our winters.) Given the veracity of this rating, I fully believe their boot a step colder is good that that temp rating. You warm blooded types can probably take them down a lot colder.
Related to boots, winter shoes and this topic - I made "gaiters" after I bought the boots to keep water from running down my tights and into the boots. (I've got long legs. The cuffs never reach the boot/shoe tops, even standing.) Bought 300 weight stretch windblock outdoor fabric. Cut a band about 7" high that fits tight around my ankle under my tights or warmers and over my boot tops. Velcro strip in back to close.
I did this for water but very quickly found that keeping the wind off my ankles meant delivering warm blood to my feet! What a difference. I now wear them with my regular shoes on dry 40s days just because it feels better late in rides.