jbulach - neither leather or cordua is intrinsically waterproof, despite the adage about cows being waterproof, both require treatments. Treated cordura is waterproof at everyday static pressures, like if you made a bag out of it and filled it, it would work like a canteen. Not all cordura is the same. Another alternative maybe would be truck tarp, which is intrinsically waterproof, but has less abrasion resistance.
In terms of cost, this came up because I have a Juki and sew enough cordura that I have rolls of it laying around. I can sew leather for that matter. Rusty had mentioned the boots were made of leather, which I thought was kind of quaint, and so we were just sort of wondering what alternatives might work. But no I never sewed one up. I don't have a deuce so I've never seen more than a picture of one of these boots.