The estimated value is an automated thing. Check out the threat "Neoitems partners with ImproveNeo" at the top of the General Neopets Chat forum to see how that works.

What we're looking for here are things that need to be added to or changed in the database -- new items that weren't announced in the News, missing descriptions from items that are rarity 99+ (the others we will find in Search Neopets), typos that we made or that Neopets fixed and, most of all, ID #s for items we have in as "searchable," "unsearchable" "unannounced," etc. Without the ID number, an item cannot be moved to "active."

Right now, my favorite typo that Neopets made is for the Quiggle Veggie Soup -- A healthy soup that is completly vegitarian and served in an adorable Quiggle bowl.