check before paying

found many cases of incidents that have been in the goods purchased can not be returned again.
This occurred in one of my friend who bought the device in a computer store in the MEDAN.
At first my friend there to check the price before buying a product here that he was looking for and finally have supplyer who sell their products with the cheapest price from a few supplyer and there were other transactions for the purchase of parts for 15 units of computers. but what happens after the check was made out of some products there is a defect. and my friend's party on the protest supplyer the warehouse but they think they have to check the goods carefully and send in the goods in good condition and there is not good communication.
so in this case we can take its wisdom "Purchase price of the goods in accordance with market prices and not obsessed with price and seek supplyer has a good image and then check that the goods are to be witnessed by the supplyer."
And by the way, was not only my friends are victims of supplyer, the fact that many are injured by their product and the fact that they are selling low end products