ampfixer
... Then the Eagles show up and sell out venues at $100+. That was the beginning of the end of my concert attendance...

You're not kidding!  I saw the Rolling Stones the same year for a "crazy" $40-$50.  The Eagles instantly doubled the price baseline for bands at that level.

grateful dead
the smiths (seen Mozza and Marr play separate gigs though) 

synkrotron
Pink Floyd, Yes and Black Sabbath with their original line-ups

The bootlegs tell you everything you want to know and experience. Given the poor quality of the recording, you have to put that aside and just close your eyes, to appreciate the performance alone.
 
PF was absolutely exceptional, far out and neat and amazing, until the original tour of DSOTM. After that, they became to mechanized, and they had no space for a little jam and fun, and I think their shows began laboring a bit. There is one exception. The series of bootlegs from the Anaheim show on the Animals tour, is totally out of this world, and you even get Roger Waters swearing at a few fans. It is an excellent concert. None of The Wall boots show anything worth while discussing in my opinion.
 
YES bootlegs were never "exciting", and I always was looking for their "Topograhic Oceans" tour for bootlegs, but never found one to listen to, though they might be easier to find now, but I do not want to take that exceptional concert at The Long Beach Arena away from my memory that still stands as one of the best concerts I have ever seen. I considered it then, and NOW, the ultimate classical music made by the folks our age.
 
Black Sabbath, for my tastes was one night good, and one night bad, depending on who was totally out of it or not. For me, the albums are better than any of their concerts, and I don't even remember looking for any of their bootlegs.
 
That's as much as I know and can tell you, and it might not be perfect. Hearing, nowadays, the Anderson, Wakeman and Rabin show, is kinda nice really, as Rick is outstanding all show long, and gives you an idea how he performed in those days ... extremely well.

bapu

synkrotron
Pink Floyd, Yes and Black Sabbath with their original line-ups

For me two out three ain't half bad.
(Never saw PF in any carnation)

I saw Yes a couple of times, both times Wakeman and Howe were in the band, so not the original line up but I would say the "classic" line up.

Pink Floyd was the notorious Knebworth gig where Roy Harper smashed up the dressing room and Richard Wrights Hammond was out of tune, not their best performance by all accounts, I recall being a little disappointed at the time. I would have liked to have seen their early shows and also in the "Pulse" era.