Due to the component supply chain issues manufacture is seriously constrained. Demand isn't, so the Law of Supply and Demand tells us that prices increase, decreasing demand and (normally, but not in this case) increasing supply until supply equals demand.
I bought my R used mint in 2018 for 201,000 and sold it yesterday for 150,000. New R's are still for sale but with a 3-month backorder at Japan's biggest electronics chain Bic Camera. I cannot believe it held value for so long when the R6 and R5 have such good AF and IBIS, but then again they cost far more.
Prices went up 10% across the entire Canon product line in Japan around April 7 or so, and I ordered a 100-500 with minutes to spare before the price hike. (Just wish I had ordered some more stuff too.)
More generally, we have to assume these people are experts in their narrow field and to say "How the heck do some sites expect to shift stock if they keep doing that?" is basically saying that you somehow understand their business better than they do. I don't go around insulting people like that, but you be you.