totally depends on what backhoe, who made it, and the build quality of the buckets. Could be anywhere from $400-$800 for the bucket and $650-1200 for a thumb.
Sales / Computer Support Messick Farm Equipment www.messicks.com
A new bucket from Kioti retails for $233 plus shipping. Have not seen a thumb attachment built for the Kioti Backhoes yet but we do have a local machine shop that can produce anything that we want.