Is it permissible to buy one gram of gold for 200 Saudi riyals, knowing that the seller bought two grams for 400 Saudi riyals, while the current price of one gram is 160.77 Saudi riyals, and is this considered riba (usury)?

It is permissible to buy gold from the aforementioned man at the agreed-upon price, whether it is more than the market price or not. This is not considered usury (riba), provided that the price is paid at the session of the sale contract, due to the saying of the Prophet, peace and blessings be upon him: "If these types differ, then sell as you wish, if it is hand to hand."