Mobile devices - phones, tablets, and laptops - are physically hard to assemble just due to the small form factors involved and the special tools needed. If it's a newly designed/patented device, especially by a proprietary company like Apple, spare parts on the open market will be hard to come by. The so-called "hackintosh", where mix-and-match PC parts are used to make a computer which can run MacOS, has been around for some time, but once the hardware is assembled which can run an existing version of Apple's OS, it often happens that a patch or system software/firmware released by Apple will cripple your hackintosh creation. It's consequently rather an expensive, time consuming hobby. You might actually save a little on hardware costs, but once you factor in the hours of time needed to construct and maintain a functional, up-to-date computer which will run a current MacOS release, the little saved on part acquisition is much outweighed by the labor outlay. Apple phones and tablet hardware upgrades, along with iOS updates, occur so frequently as to make assembly of a "hackinphone" a losing proposition. As Dan mentioned above, do you really have the time, money, and language skills to go to Asia to chase down parts?