I bought 3 different sizes. The main board that you see in most of my pictures is 24"x72". I also bought two smaller sizes that I can use for smaller assemblies while the main board is in use for other things, those sizes are 12"x36" and 12"x24". All of them are 18 gauge steel and they cost a total of $42. With the cost of the magnets, the wood for the fixtures, the steel, and the misc. nuts and bolts needed the cost was somewhere right around $200. At airfield models he used an additional piece of steel to store his magnets on when not in use. If you look at the pictures of my system in the build thread I use the side panels off of a computer case to keep my magnets on. My wife and I own a computer shop so we have lost of old cases around, so I used those instead of spending money on another piece of steel.

Ken