My AFO is a plastic one and it was molded to fit my foot and leg exactly. It had to be refitted several times before it was a perfect fit. It must be exactly right or you will get pressure sores in any area it does not fit really well.
Mine is an articulated brace and it has moving parts that pop the foot up, these parts are key to the function and they are metal. I can imagine that part maybe being titanium and lasting well because of it.
All that having been said, I find my AFO does not help much. It will not help your leg bend at the knee and if a big part of the problem with your walking as it is in mine, you may find that it helps not at all so, try a loaner before you pay big $$! Mine sits in the closet.