440Source has fabricated valve covers for $170. Fabricated valve covers are made from sheet metal that is welded together. A billet cover starts as a big chunk of aluminum and then the valve cover is carved out of it. Totally different process. Some high end fabricated covers are made from a mixture of billet and sheet metal. I've seen SBC covers which use billet ends and a sheet metal middle. That is a nice way to get the complex shapes in billet but the flat shapes from sheet material.