From the 1st instruction link (HobbyLobby), about 9xlength of the headband (single ribbon). Plus the ribbon to wrap the headband. So maybe 12x14"=5 yd!!!
But if you purchase UB ribbon? How much for 50 yds? $2?
It's super easy but time comsuming since you have to braid it loop by loop.
I don't think it's a good product to bring profit. Just for entertaining purpose--make one for your little girl
And your post remind me that somebody don't have ribbon and headbands. Just add an ad in the original post