Higher Price for Late Payment Without Explicit Mention

The supplier knows that I lack liquidity and I always buy on credit and pay after selling the goods. Therefore, he always gives me a higher price than he offers to a merchant who always pays in cash. However, the supplier does not explicitly state this. It should be noted that the contract with the supplier is personal, and each merchant receives a different price from him based on the quantity of goods, seniority, and other varying conditions. However, it is clear to both of us that the method of payment is a central reason for the price, even though it is not explicitly stated.