In what way can you show your customers that your services or products are worth the cost?

One has to be very polite and has to play very smart with the words while explaining the product one has to keep in mind the grey area of the products and the competitive rebutuls more over that one has to be focused about the best part of the product and he has to smart enough to moulde the customer in his kitty by his communication skills and for that has to be best at knowledge about the product and specially the best part of it and has to highlight the unmatched bets part of the product while explaining it to the customer