Don't say:
What's the cost of this watch?

Say:
What's the price of this watch?

Note:
Value is the usefulness or importance of something The value of milk as a food, the value of education. Face value is the amount printed on a piece of-paper-money or on a postage stamp. Price is the amount of money paid by the customer Cost is the amount paid by the shopkeeper We can say How much does it cost?