Is it permissible or forbidden to increase the price of an item one buys for 30 Riyals and sells to colleagues for 50 Riyals, based on their request and need?

If you are an agent for your colleagues in purchasing a commodity, it is not permissible for you to increase its price for your own benefit, according to the Permanent Committee's statement: "It is not permissible for an agent to take anything from the principal's money except with their permission." The correct way to profit is to be an agent for a known fee, or to buy the commodity for yourself and then sell it to them for an increased price.