How to verify if it is scam? It is an open dealing area where the onus is on each of seller and buyer.
I would exercise some common sense about it and if it is too good to be true, then its better buying it from someone else who sell it at a price which most other is selling. You are not obliged to buy from anyone, best to have money remaining in pocket and save for a safer deal. If all else fails, then spend longer to save up for more and get first hand from the reputable shops.