All distributors give a certain amount of profit to the retailer as we all know, for e.g. Oppo gives a straight profit of 5000rs to the retailer on their phones. What hsn does is cut down on their profits to attract buyers with the overall lower price in order to move items quickly, but that's just my theory.
The 4c is a newer phone, so it being a used or refurb peice is not possible. Third, when the phone comes with an official 1yr airlink warranty, then it has to be legit. Airlink would not provide warranty on a used/refurb item. The phone would also have a sticker saying "Approved by PTA" meaning it's legit.
I sometimes buy branded watches from them too, and most of them are 2000-3000rs cheaper than the market while still being original. And they arn't even expensive watches, all are sub 10, 000rs.
Again I cannot confirm anything as I'm not associated with them, Im solely talking from experience, rest Allah knows best!