Is it obligatory to pay the remaining money to the seller of prohibited steroids after repentance?

If by "stimulants" what is meant is sexual stimulants, then their ruling has already been explained, including when their use is permissible and when it is prohibited. If something else is meant, then it should be clarified. The Shariah permits the use of anything that does not cause harm, contain anything prohibited, or serve as a means to a prohibited goal. If the use is permissible, then the remaining money is the right of its owner. If it is prohibited due to an incidental factor, but the substance itself is originally permissible, then its sale is permissible and its price must be paid. However, if the substance is prohibited for use and sale, then the remaining price should be given as charity or spent on general Muslim interests and not returned to the prohibited seller, provided that this does not lead to a greater evil.