@Alex-dono-sama back when he was creating bows and the pipsqueak master was breaking them, he says there is a lot of feathers to use, so I think every time he makes a bow he "consumes" the feather, and when he dispels the bow, it's gone. If I remember correctly, his master uses that pocky-thing in her mouth to create a bow, so she must carry a large amount of them all the time to create bows at the drop of the hat, while Iruma uses the feathers of the Lord of the Valley as his source material, so it should be a very limited amount.