There are very few modern children's books that have any monetary value once it has been processed and subsequently discarded from a library. One exception to this rule is:
SINBAD and ME by Kin Platt. Phila: Chilton Books, 1966. Great juvenile mystery about a boy and his bulldog Sinbad. Won the Edgar for best juvenile mystery. I loved this book as a kid and enjoyed re-reading it as an adult.
Not only collectible as a library discard, the last time I checked the Tempo paperback was going for $80 dollars or so in Very Good condition. It's also very difficult to find.