Out of curiosity, I looked on Hemmings.com for MGBs.
90 of them for sale, I filtered down to 18 private parties to eliminate dealers & auctions.
I didn't look closely at each one, but $8,000 - $20,000 was the range for what appeared to be decent to excellent.
Under $8,000 were the obvious crap-boxes; you decide on the upper end whether those are the best ones available, or dreamers.