Estate sales and thrift stores often have what I call "random pricing."
I used to have really poor luck with estate sales where I lived several years ago; anything technology-related that fell in the kinda-old-but-not-collectible category like a typical 70's TV or radio was usually way overpriced. So, I tended to avoid estate/tag sales. [Estate *auctions* were generally better, because the price was dictated by actual demand, so if you were the only person actually interested in a given item, you'd likely get it for a song.]
However, where I currently live, the local estate/tag sale companies seem to generally have more realistic pricing. What's kinda funny is that one of these companies also has an antique store in town which is a rather spendy place specializing in 50's/60's pop-culture and such. They do tend to have pretty good quality items in the store, but at a price. Prices in the store start at "high" and go straight up from there. So you might guess that their estate sales are overpriced. As it turns out, that's not true at all-- the pricing at the sales they run is usually quite reasonable..!
As for wildly overpriced modern TVs and the like at estate sales like the ones jstout66 keeps encountering, I'm surprised that it would continue for so long-- I would think that a problem like that would be self-correcting. After all, the estate/tag sale company doesn't make a commision on the item if nobody buys it. It's in their own best interests to price things so that somebody will be likely to buy the item (while still trying to maximize the price it fetches). If these people run estate sales week in and week out, they should know by now that the likelihood that someone will actually pay $400 for a 1990's-era 25" color TV (even if it's a high-end model from that era) is basically nil. Same for a $60 13" modern color portable with no remote.