It is possible to do this type pleats by hand for a very short length. I did these by hand.
I chose a brown grosgrain ribbon for the band and decided I wanted a pleated grosgrain ribbon edge. I only had the wide grosgrain which would have been too wide for the edge but if I pleated it on a bias that would narrow it down and give it an interesting edge.
To make the pleated ribbon decorative edge I made a cardboard measuring tool.
The end is at 45° and there is a clip every 1/2″ on both sides.
With the guide I could make a series of lines across the ribbon every 1/2″ very quickly.
Then I pressed the pleats into the ribbon along those lines. The pen is a heat away pen, so they disappeared as I pressed.
I needed ~48 inches of the trim.
Finished hat; I adjusted the trim so that more of it was on the inside brim than on the outside edge. Making these by hand was not all that difficult because they are wide and there are not all that many. I could never see doing as many as there are on the gray hat by hand.