What is the ruling on coordination between a buyer and a seller and agreeing with each of them on a different price (for example: buying at 100 and selling at 150), then receiving the amount from the buyer and handing it over to the seller without paying anything?

It is not permissible for you to sell a commodity at a price higher than its real value without informing the buyer that the increase is your brokerage commission, or without agreeing with the seller that any amount exceeding a certain price is yours. Similarly, it is not permissible to mislead the buyer with an unreal price or to tell the seller a price lower than the actual sale price. For the transaction to be valid in the future, you can purchase the commodity and then sell it without mentioning the original purchase price.