If you're looking for Sunfish books, get them from the Class Office for $30, don't go to Amazon. The used book dealers think that the books are rare, and are charging accordingly.
The high Amazon prices for the three are as follows:
Sail it Flat: $125
Successful Sunfish Racing: $189.50
The Sunfish Book: $110
The Sunfish Bible (all three books under one cover) is fetching a whopping $213!
I have the three books, maybe I can sell them at these prices and get the Sunfish Bible and a new sail!
All books go "out of print' as a publisher will set up a printing run of 'X' number of books. If the original three books now composing the Sunfish Bible are never going to have another printing run as separate books they may have some collectors value. As you both have indicated, the asking price sounds greatly inflated. Maybe $50 bucks for all three books as a set.