I made this project because I needed a toolbox big enough to bring my drill and assorted hardware when working outside my house. I thought that this was an elegant design and especially liked how the lid is attached to the toolbox. It is a simple and elegant solution. The only divergence I made from the original was to eschew the use of a diagonal on the top. If you look at a picture of the toolbox in the closed position you will see that it forms a perfect surface to saw 2X4's or other wood. I can jam the wood up against one of the pieces of wood and it is very stable. I can sit on the box. I've even used it as a stepladder of sorts (upside down) in a pinch.
The total cost for new materials was $22 but that includes a big piece of 12 inch board that I will use for another project. If you pro-rate it for usage the total cost of new materials is $16. The total time for the build was about 4 hours, but that included drinking a beer.
I really encourage you to read the resource above as it is well-done and has the exact dimensions for the wood cuts and directions for the build. What follows is a synopsis of the build.