Those phones from the Chinese shops

I want to get a iPhone 7, they’re €779 from the apple website and are the same price with Vodafone, slightly cheaper on meteor at €750.

I seen on adverts that the Chinese shops are selling these phones for €650 and are stating the phones are new, unopened in the box, sim free and have a years Apple warranty.
Seems really good to be true.

How could they be that much cheaper? Are networks and Apple online really ripping everyone off or is there something wrong with these phones the Chinese shops are selling them for? Are the phone clone phones or maybe stolen and modified to be unlocked maybe?!

I’m assuming a lot here but was wondering for peoples input before I fork out €650. Anyone have any experience with buying a high spec phone from these shops?