Thin gauge aluminum, such as .040", will tend to look wavy. Heavier aluminum would work.
Or, the inexpensive brands of aluminum composite material with the solid core might be a good choice. Polymetal, Maxmetal, Bebond, etc., are all rated, I believe, as five-year materials. The more expensive brands of ACM can carry a 15-year, or more, rating, assuming you can provide graphics that will last that long.
Regarding Alumalite, I do not like the way it dimples from screws, which gives it a cheap look. I have also seen it delaminate sooner than I would have liked.
One way to offer two prices would be to give the client two differently priced designs. Better design work should always command more money, remembering that we are not selling signs by the pound as if it were hamburger.
A doctor once said, "You're not paying me for my time, you're paying me for what I know."
This should also be true if you can offer superior design.
Also, "installed" versus "uninstalled" would be a way to offer two prices.
I know many are in the habit of giving nonprofits special pricing, but I have never given price discounts to companies simply because they are nonprofit. I prefer to price the job as usual. Then, if I felt the nonprofit was for a worthy cause that I wanted to support, I gave a donation. This allows you to keep a better handle on charitable giving. Besides, I believe a gift of money is far more appreciated than a discount. And if I can't afford to give them money, then how can I afford to give them the discount? There is really no difference, even if it feels like there is.
Brad in Kansas City
