Expensive? Yeah. but NOT as costly as cutting off a thumb or a kicked back 2 X 4. This is designed to support whatever you're cutting, so you can SAFELY keep material under control. It is well made (albeit in Taiwan) with heavy- duty parts -  rods, plates and hardware. Mine came with STANDARD 1/2" SAE nuts. Try using adjustable wrenches to install the rods to the plate and the screws underneath.  Also if you leave just a little looseness in  the installation hardware under your saw, you can easily slide the extension in and out to accomodate your lumber. You may want to lightly lubricate the rods. If I had a complaint, it would be that this should come WITH your DeWalt miter saw instead of as an extra.