What is the ruling on a merchant selling a product that he purchases from the internet to a customer with an increase in its price, either by increasing the exchange rate of the dollar or by selling the product at a higher price than he bought it for?

If the questioner purchases the commodity for his own account and it enters his possession, he may sell it at the price agreed upon with the customer. What transpires between him and the customer before he purchases the commodity is a promise to sell, not a binding sale. However, if the customer pays the full price and the commodity is something that can be precisely described, the sale is valid as a salam (forward sale) contract, provided that the commodity is delivered at a known future date.