Is it permissible to sell a perfume for 15, when its original price is 10 and it comes with a gift, to someone who ordered it after being informed of the higher price without mentioning the gift?

If you are asked to buy perfume, you are a trusted agent, and it is not permissible for you to take an extra amount from the seller beyond the price of the perfume or the gift, as the gift belongs to the principal. Similarly, it is not permissible for you to buy from yourself. However, if you buy the perfume and then sell it to them, you are not obligated to give them the gift, and it is permissible to sell it for more than its price, but it is not permissible to lie when asked about the purchase price.