There are certain very early MTBs that may get a special following and sell for far more than one might expect.
But, I have to agree.. that $1100 seems a bit high.
I have seen a few flippers on Craigslist. There was a very rough Peugeot PX10 on Craiglist for $75... try as I might, the seller was very bad at communicating. Never giving a phone number. Saying things like "Let's Meet", but never specifying where.
Anyway, a few days later, the bike popped up for sale for $300, I think. It still might have been an ok deal, but the bike was very rough, and I was offended by the whole process.
There probably have been a few bikes that I could have flipped with minimal effort... if I wanted to.