Here’s a quick and easy way to make a homemade honeycomb-type grid to control the light emitting from your soft box.
1. Visit liquor store and get some boxes with inserts (dividers). You may need to get several depending on the size of your soft box. And, depending on your desired degree of light output, you may need to modify to the grids by inserting pieces of cardboard to tighten up the holes for a more controlled light source.
2. Spray paint them black to help control the spread of the light and also the color temperature.
3. Depending on the size of your soft box, you may need to hot-glue the box inserts together at the ends, or find another way to attach them together.
This method will of course be more cumbersome than the $400-and-up purchased ones, but can do the job just as well. And they fold up easily for travel or storage.
Example of Chimera light modifiers: http://www.chimeralighting.com/Products/Light-Modifiers/Lighttools-Soft-Egg-Crates-Fabric-Grids