I guess there are some privacy concerns, it being a Chinese company, apart from that looks a good deal & one of the best phones available in the market right now at that price range. Like your cousin says, the fact that so many of the parts are bought from them, they are able to produce at prices that no one can really compete at.
Though with
Moto G reducing prices (plus 10% cashback with SBI cards) , I would say it is probably a safer bet. More so, with regular updates & stuff.