Vinyl pressing mistakes

In the early 1980's my old chief inspector gave me an mislabel LP. He purchased 1974's Valentin Baglaenko "Gypsy Songs And Ancient Romances" for $1.99 but what was cut in the grooves was The Grateful Dead "Best Of"? "What the hell is this... high on cocaine..." was his reply when he gave me this record explaining to me the relax mood he was in that night.

I had a pressing of the Stones "Some Girls" that had a side 1 label on both sides.
I thought it may be worth a zillion dollars at the time.
I ended up selling it with a bunch of other LP's.
I guess I'll never know!

Funny. Just got a LP totally covered and sealed from a record store and guess what? It's 1976 album reprinted on 2008 that has a different artist/album side pressed on the b side. I listened to the a side of 'Legalize it' by Peter Tosh.... flipped it over and Nat King Cole 'LOVE'. I thought it so cool that I decided not to complain and keep it. :) 

BTW, wondering how much this might be worthy nowadays? :) 

Could be worth a fortune to some eccentric collector, like the famous air mail stamp from the 20s, with the upside down airplane.