Is the sale and purchase considered valid if 10 tons of iron were bought at a low price with an agreement for it to remain in the seller's warehouse, and then its price increased later and it was collected?

The sales contract is one of the binding contracts, and neither party has the right to revoke or amend it except by agreement. The increase in the price of the commodity after its sale does not affect the validity of the contract, and the seller does not have the right to the price difference. If the commodity is sold for a dinar currency, the seller is entitled to the like of his debt, not its value, because debts are settled by their likes, not by their value. The transaction between you and the iron seller is valid, and you are only obligated to pay the agreed-upon price.