Yet more, fake/cloned, S4's.
Not only do they work but they come fully boxed with accessories just like the real thing, as this video shows...
FAKE Samsung Galaxy S4 GT-I9500 Quad Core Unboxing - Replica - Knock Off - Clone - YouTube
The above retails at £103GBP, US$155, €118
Again, this shows a working fake...
Samsung Galaxy S4 clone First Handson - YouTube
However, all is not lost as there is an app, free, from the Play Store that can be downloaded to determine the authenticity of most of the popular S4 models... GT-I9500， GT-I9502, GT-I9505, GT-I9508, SCH-I959, SGH-I337, SPH-L720, SHV-E300S, SGH-M919
It is the Genuine Galaxy S4/S3/Note II
that checks the phone's details and hardware configuration and also runs performance tests and compares with other phones in the world.
Whilst it cannot prevent anyone buying a fake S4 it can at least go some way to determining if a phone is fake or not without having to ask a lot of questions.
For anyone thinking of buying a phone from the web or, indeed, any untrusted source, the watch words are...
... Let the buyer beware!