I've never done anything with leather before, but my daughter would not let me crochet a pirate hat for her. I found instructions for a Jack Sparrow tricorn hat on Livejournal and cut the cost by using a ruined leather jacket instead of the new leather called for. Because I was using a jacket, there are a few seams in places where they shouldn't be and I had to back the leather with fabric so it wasn't quite so floppy - but it turned out pretty well - and it's free. The used leather was also easier to work with - I could use my sewing machine on it. As a bonus, I'm making the remainder of the jacket into a buccaneer vest to add to her costume.
Aargh - I would add the link to the original instructions, but I can't find it again.