I'm not saying NVidia sales are slowing down (the books are complete for quite a while AIUI) but... Where would we hear first about a slowing down in sales? From a NVidia quarterly statement or from the market of renting GPU compute?
Used GPU prices still seem to be pretty high and availability is low? But yes, if the GPU compute rental market is highly unprofitable (I'm not sure it is, though) while HW prices are still high that indicates a clear inefficiency in the market. Meaning that you should sell ASAP before it self corrects.