Samsung recently formally announced the Galaxy A3 and A5 smartphones, but they’re currently slated for a relatively small Asian release with no concrete plans on bringing them to other markets around the world. Apparently, a big reason behind that is due to Samsung’s low yield on production of the unibody metal frames for the devices.
With these phones being among the first full metal Samsung devices with no removable batteries, production for components was a little different than what Samsung was used to. Reportedly only about 50% of the cases made it past Samsung’s quality control, which is a very, very low yield and explains the limited availability.
Samsung is a huge company, and there’s no doubt that the yield issues will decrease as they make more and more devices like this. For the time being, though, expect most of their mainstream devices to take a Galaxy Note 4 approach and mix metal and plastic.