Even the ludicrously priced mice which I have been guilt of buying myself often are all made of the same cheap plastic components glued together.
not all. my old Trust mouse had a metal axis for the wheel. it was visible from the sides. anyway, i managed to fix it. the plastic part had hexagonal shape, so i got one of those hexagonal screwdriver things at the right size, melted the plastic contact point of the wheel and put it in to make it like one body, after it solidified, i inserted the input device and cut the rest of the tool. i then put it back in it's place in the mouse and now my wheel has a metal axis