Lego Chess Set - motorised, $32k, 100k bricks
Check out the detail on the pieces, I love how the knight's legs move as it travels the board. Though I was really confused until I realised they HAD to move the pawn out the way before the knight could move.
The whole lot took a year to plan and build, led by 4 main people and helped by 23. Their site has more stats on how it was done and what it involved.