Actually a hundred for a 939 in good condition is about right. I have a mint Pioneer SX 780 and am looking to get some Dynaco A 25's for my computer room. The A 25's were my first hi fi speakers worth noting back in the early 70's. The 939 is thirty years old but this stuff was made very well, which is why there's so much of it still out there working fine. Here is classicaudio.com's valuation and info: http://www.classicaudio.com/value/pio/index.html
They sell for about 80 to 160.
You guys should see what top of the line receivers like the big Marantz or two piece Sansui receiver go for in nice shape. Would you believe 2-3000 bucks. These things were putting out 250 to 300 wpc and still work good. I'd go so far as to say they're built better than alot of high end gear made today and feel that I made an accurate statement. What's amazing is the sound quality isn't near as bad as one might think considering all these great advances we've made over the last quarter century, or so we're told.