The high priced speculation in Newbery and Caldecott Award books is a relatively new feature of the in print collectibles market. While some of the price increases can be attributed the the high number of dedicated and active Newbery and Caldecott collectors, a lot of the increase results from book publishers being less and less willing to print large runs of juvenile hardbacks. Also a factor is that if a book is successful and sells well, there is a very good chance that it will be in a later printing by the time the awards are announced. In the last decade or so all these factors has driven the prices of the award books up accordingly.
The first book I recall selling for around two hundred dollars within a week of the award being announced was The Giver (Newbery 1994). Some of the other titles that were difficult for me to find in collectible condition: Smoky Night* (Caldecott, 1995), Out of the Dust (Newbery, 1998), Holes (Newbery, 1999), Snowflake Bentley* (Caldecott, 1999), A Single Shard (Newbery, 2002 ), Kira-Kira (Newbery, 2005), and last year's The Higher Power of Lucky (Newbery, 2006).
*Publishers tend to have larger print runs of picture books than juveniles so it takes a real surprise by the Caldecott Award comittee to result in a scarce Caldecott winner.