Nicest Fly Baby I've ever seen changed hands for about $15,000. Same basic airplane, just low wing.
Most expensive Fly Baby I've seen was listed at $24,000, but had an engine that didn't have enough power. Believe it went for far less, and the new owner is replacing the engine.
Fly Baby is a close equivalent of a Pixie, though some Pixies have VW engines (which should reduce their value).
Single seat airplanes are difficult to sell, too.
Not actually haven't seen the airplane, I'm reluctant to estimate, but think Dean's $10K-$15K is probably a good guess. I've seen flyable Fly Babies in the ~$8,000 range.
Ron Wanttaja