Why the difference in resale value?

Weird, as Nelson Pass designed the Adcom GFA555

I bought an Adcom 555 brand new from Tweeter HiFi in the mid 80’s.  I couldn’t wait until I could afford something better and never liked the sound.  I do not see why the love for Onkyo. At one time I sold the line and it was real junk, broke down often and sounded like nothing special.  While the Onkyo may have looked good on the outside, the inside was full of cheap parts, internal heat sinks could cut your hands to ribbons.  

P.S. I said I "enjoyed the heck out of" my original Adcom GFA 555. Thinking back -- it was a long time ago -- that really isn’t true. I remember that the treble always bothered me, Nelson Pass influence notwithstanding. I sent it out for modification and finally sold it. After an intermediate amp that sounded better but had transformer hum, I wound up with a Bryston 14B SST, which was another, far better, world of high fidelity. Better across the band!
I've never tried an Onkyo.

@mike_in_nc I have the 535L. I cannot be sure if it's Pass designed or not. I love the bass and the slam but the treble is a bit rough. Same experience. Bought in early 90s.