We've discussed this numerous times on the phone and at NEAR-Fest, Mike. Values overall or on average are indeed down and will continue to drop as supply overwhelms demand going forward. The fact that a clean, late/limited production, or other odd piece brings a high price doesn't change that. As long as there are collectors looking to add to or upgrade their collection, that will be the case.
I saw a time when those tuners were bringing a kilobuck, sometimes more. Same with $2500-$3K round emblem KWM-2As and so on. It was the rule then, not the exception. Average price now seems to be in the $500-$800 range, as we've discussed. Same for the $1500 32Vs and so on. No speculation involved, just cold, hard data.
Ebay is not and has never been the average market. It's always been the high water mark, biggest audience and therefore, exposure to the deep pocket folks. It's a great place to sell if the promise of a few more dollars offsets the hours spent dealing with listing, packing, shipping, and whatever other issues arise. I've used it successfully over the years in just such circumstances. But far more of this stuff sells at hamfests and privately for much, much less (as you yourself have personally experienced and benefited from). And even on ebay, prices will continue to reflect a lessening interest over time along with more immediate factors like economic conditions. The few clean or exceptional items won't change that.
Congrats on getting $600 for your $1200 tuner. Of course, your savvy business skills realized a profit, even in the softer market. We're lucky to have gotten into this when we did, for the reasons we did. Anything after is like skimming the cream off the top.