I don't think there is any question that the trend is downward. But, the question is abut the current cycle. Sales are very slow, possibly slower than they were after the financial crisis in 2008. How is that possible? I personally believe that most sellers are wildly over-optimistic in setting their prices. I am always surprised to see items I sold 7 or 8 years ago routinely listed for 50+ percent more than I sought. Part of that is the growth of dealer listings. I do see well priced, popular items selling in a day or so.
If you are not in that category, well, you might as well be playing the lottery!