Boy, that is a lot tougher question than seems at first glance. I saw this thread several days ago and am still struggling. All the real top contenders are speakers. Is a 3-way tie list cheating? Ok, I’m going to cheat..twice maybe..
Best Buy for the $ is Used pair of Energy 22 reference connoisseur speakers, heard in 1984 but purchased in late 90’s if can only pick one. I can think of several pieces of gear bought new in much more recent years that are tremendous values to me, but hard to compete with something that was a good audio value even new in 1984, but bought used at about 1/4 the original price is hard to top.
As for worst buy, that is really even tougher, requiring more thought. I put a lot of time researching before buying, back in pre-internet days using “The Sensible Sound” magazine as my guidepost and bible, kinda like ASR forum in the modern era.
I saw the Mapleshade reference in the prior post, and going to take a wild guess—could their cable “trestles” be what someone is referring to on the worst list? I’ve never in over 50 years in this game purchased a Gucci cable, using nothing beyond a well made basic cable. I’m betting no one would admit it here if their worst buy was some $1000 cable. Heck, right now I’m using a $10 Monoprice XLR cable to feed a $3500 Benchmark AHB2 amp.
I’ll come clean on the worst part when I can figure it out. I guess I’ve been really lucky in that something really bad doesn’t quickly come to mind.