You can make one of those for cheaper. Using the book Im about to mention.

Id get a book called mini weapons of mass destruction. Both of them. And then office supplies to build your armory. I have hours of fun with this book, making penile catapults, paper clip trebeshays (dat spelling doe), and other things. Its not $150 but is still pretty damn cool.

Alternatively, or along with it, puzzles. Surprisingly enough, rubix cubes are not as hard as everyone says, and are great entertainment when you get good at it.