I work for a Shoe manufacturing company. Eventhough you would be making these yourselves, I would still recommend getting "Lasts". Lasts are basically plastic resin feet that ALL footwear manufacturers use to construct
our footwear. Its what allows the leathers when Lasted correctly to form to the shape of the foot, including the size and width. So eventhough you are wanting to keep costs down. Lasts are not cheap either.
You may get lucky and find some wooden Lasts, but mainly todays footwear use the plastic resin Last. Another thing to consider is the arch support. You're still gonna have to do something there such as a steel shank. You can also use heavy leather, dried and shaped, but even those will break down. Steel is the best choice.
Where I work, www.wescoboots.com, our boots take 155 plus steps for completion and only 33 employee in the factory.
Sorry, lol, I see posts about footwear an dI have to chime in. Good Luck !! Post pics when you get sone.