This is my first year riding in winter(Commuting doesn't count). On Christmas Eve morning, I did my coldest ride yet(on a road bike). It was 0f. My hands are wimps when it comes to the cold, so for the first time I purposely overdressed around my core and went out with bar mitts, regular winter road cycling gloves(and heavier gloves in reserve just in case, and hand warmers. Wow, what an epiphany!. Although I know the basics of keeping hands warm, I had no idea that keeping your core almost hot would have such a strong effect. I ended up riding 40 miles with my hands out of the mitts for most of the ride. When I got home the temperature was a balmy 5f. Granted I was only averaging 13 MPH. Usually when I have this type of hand protection, my hands are chilly below 20f in the mitts. Huge difference! I guess the adage "dress to be a little cool when you start out" doesn't apply to my hands. FYI: Pedaling wasn't too much fun with 3 layers on my legs. I did invest in PI Amphibs afterwards. Looking for a 2nd pair of winter bib tights(I commute) that are effective down to 10f with cycling pants over the top. Options so far: Castelli Polare Due, Gore Xenon 2.0, Rapha Deep Winter Bibs(no chamois). I also upgraded/upscaled and downscaled my wallet(ouch!) for some Rapha base layers. Although I'm not a Rapha fanboy, the baselayers are fantastic!(Deep Winter Baselayer, Winter Baselayer, Deep Winter Collar. I justify these purchases in my mind by not having to buy gas as often. There's 2 things where money is no object when it comes to cycling: Safety and comfort when it comes to the elements).
Regarding cost: if you buy decent stuff, you will not be replacing it quite so soon either. I don't have experience in Rapha layers, but I use (merino) wool. Expensive, at least when compared to the "technical" layers you'll find in the discount bin, but very good. I've actually started buying thin merino T-shirts for summer conditions as well.