In all the whole thing cost about $20. Here's how I made it and what I would do differently next time...
Step 1: Frame
The amount of pipe depends on the width of your window. Mine window was about 5' wide, so a 6' wide frame was selected. A main reason 6' was chosen -- I'll say this now -- is that the awning material (canvas drop cloth) is available in a 6' width.
I would not make the awning much bigger than this without more frame support structures. A 3' gap (like mine) is about the maximum I would recommend. I base this on having watched how it handled windy days.
Don't use solvent/cement yet. You can dry-fit parts for now.