Shopgoodwill is like most of the auction sites, a few years ago when it was fairly unknown there were deals to be had, so the risk was worth it. As it matured, more bidding momentum from competing egos and the psychology of what makes over-bidding happen, and it has become just like ebay or craigslist or facebook marketplace or letgo or offerup or US Audio Mart ... many buyers trying to get that one item drives the prices up to a point where the risks often outweigh the deals.
Again like the other sites mentioned, local can lower the risks, and just letting the mediocre deals get away and waiting patiently for the remaining good deals makes the difference. On SGW there are many (surprised this wasn't) pick-up only sales, these are often the better deals because it attracts less bidders and you get the chance to actually see what you're buying. I haven't bought equipment from any of auction sites in years, if I can't see it before I buy it I probably am not interested. Bartertown here is a very small offering and small market, but since there's a forum here for feedback the "flippers" on BT are typically held to a higher standard and most if not all deals go well, just hard to find the right gear nearby (and nearby for me might be Detroit, Indianapolis, Toledo, ... within a few hours' round-trip).
From what I can see the SX-1250 on SGW was in very good to excellent cosmetic condition, worked, and since it was donated it is IMO likely that it was from someone who didn't understand enough about vintage audio to have muddled around inside. This is a premium buy for me, exactly what I look for, I would have paid top dollar. I think $2,500 is still high, would expect a box and manuals for that, but if that's the model I want then I know it might be a year or more until there's another one that nice (and what will the price be in a year or two?) so you pay what you have to.
