Roughly a 30" square piece of polyester satin lining fabric. Side edges hemmed. Top hemmed to make a drawstring pocket.
1 yard length of silver cord.
No need to hem that bottom edge... leave that salvage (if in good condition) as intentional fringe. No one will know the difference.
Knot the ends of your cord so they don't unravel.
1/2 a yard of fabric for $1.25, 1 yard of silver cord for $2.
Super hero cape (or devil, or magician, etc) for $3.25.
More on all this later. Seriously. A lot freaking more.