Why Crazy Prices paid for Pioneer 100 JBL L100 AR1 AR3 AR3A

I have owned AR-3ax, AR-4x, JBL L100, JBL Decade36 over the years. I still have AR-4x and Decade 36. These speakers have the same sound as their siblings for WAY less money.

The nostalgia craze hits most hobbies after 30- 40 years. Anything that was desirable when people were growing up becomes attractive when they are older and have money. Try buying a vintage 70s muscle car these days! Old crap receivers are going for more money than separate amps and pre-amps of the same era. Garbage turntables are being gobbled up, when true high quality ones remain unknown by the masses. LPs are in demand and prices are crazy. Big brand speakers like you mentioned are the rage -but were not always the better performers of the day. They were what the masses wanted, but most could not buy. People forget that most of the old stereo gear they lusted after in their youth was made cheaply to sell at places like JC Penny’s, Macy’s and at the hi-fi chain stores. Most of the low to mid level big brand stuff was mediocre then, and not worth the asking price today -if it’s my money. But you have seen the prices people get for it, and nostalgia is why. If you have any of that stuff to sell, now is the time. This will all end as new fixations pop-up as the nostalgia timeline moves forward. Don’t sell off your CDs! They will be the rage again soon🤑

I have one pair of AR 3 and one of AR 3a, and have listened to neither yet because they were rescued from a recycling place and I want to rebuild-them-some-day.  The AR 3 (early ones) have two salient features: AlNiCo magnets much heftier than later models, and at least very early ones had cabinets made of a Navy post-war overstock of teak wood or some wood very dense and impervious to the elements. 
As for the JBLs, I recall they were great for disco music but not really suited for classical music - maybe for jazz.  They were great in their days, but if one could show me a JBL Paragon system, now that was the nec plus ultra then, and perhaps even now, with all due foam and crossover rebuilds as mandated by all these dinosaurs. 
Pioneer? I had a QX-949 pseudo-quadrasonic, or tetraphonic (but not quadraphonic, a misplaced, mixed-roots neologism, as marketing mavens lured us to remember the technology). I said "Meh!" and sold it.  I preferred my Kenwood KA8006 and KT8007, very elegant design and I think at least equal performers to the aesthetically boring Pioneer corresponding amp and tuner.  Not to speak of my unequalled Marantz 2275, or better yet my 2270 (two phono inputs awaiting my Empire 498 and B&O 4002), which are awaiting the same fate as my ARs some-day-soon. 

Lots of reasons.   Quality, nostalgia, balance.   Back in the day, both the JBL L100 and AR3a were reference speakers, albiet for different purposes.  Both were descended from a family of speakers that set new standards for performance, and both speakers are regarded as points in time when everything fell into place.  A true whole being greater than sum of parts.

The JBL L100 was a consumer version of the primary studio monitor in use by top Rock and Pop Music studios.  You were literally hearing the same sound as recording engineers !  Combine that with bold styling, punchy bass and relatively high efficiency and you have a speaker that inspired wet dreams among pre-teen boys, at least until they discovered girls, then the speakers were a means to another end.....   If you like classic rock from 1965-1980, then you will love this speaker.

The AR3a was a redesign of the groundbreaking AR3, which was the first speaker to use dome midrange and tweeter drivers.  There is some controversy, but AR is believed to have invented dome drivers.  The AR3 offered true 30hz-15khz frequency response, with minimal distortion, and wide dispersion that modern speakers struggle to match.  Competing speakers were twice as large, and struggled to go below 50hz, and above 10khz.  At one time AR had about 30% of the entire speaker market.  The 3 and 3a rewarded serious listeners.  They were simply the most accurate speaker one could buy at the time.  They were true reference speakers for jazz and classical recording engineers.  They were used for sound reinforcement when backing acoustic instruments, ballet, recitals etc.  "Serious Music".  They were not rock speakers and that led to seeing their market share slip away as the market changed.  

AR speakers were designed for mid -far field listening...about row 10-15 in a concert hall.  They sounded best in a moderately sized living room, about 10-15 feet away from the listener, playing acoustic instruments.  Used within their limits, they sound wonderful even today.   The problem is the newest example is at least 45yrs old, and most are 50yrs+.  The suspensions of the mid and tweeter domes dry out over time, and the level controls become corroded.   There are people that can rebuild the dome drivers, and there are drop in replacements for the level controls.  Once serviced, one would be very surprised at how good they sound even today.

I owned a pair of AR3's for about 5 years(years ago.....don't remember exactly but probably in the early 1970's)....sold them and bought a pair of original Quad ESL's from Jonas Miller in Los Angeles. The first piece of classical music I played was almost not recognizable....the Quads were that much better than the AR's