Is this stuff just for costumes, or is anyone really wearing maille as armor today?
There are several modern non-ornamental uses for maille. Butchers and shark-divers often use a specially designed, welded maille to protect their skin. An extraordinarily large version of European 4-in-1 weave is used to protect highways from rockfalls from overhanging cliffs. The SCA and many other re-enactment groups still use maille as actual armor for various types of medieval martial contests.