All you need is an old adult size shirt and a pair of scissors
You can use the front of back for the cape. The side that you want for the cape cut as you see the red lines, then flip the t shirt over and cut around the collar like the blue line
And there you have it! Easiest cape ever. My kids play with these ALL the time.
Totall Cost--FREE. Who doesn't have an old t shirt laying around?
If both sides have print you can turn it inside out.