What is the ruling on the excess amount ($998.25) over the value of the shares that the bank deposited into the customer's account, knowing that the bank informed him of an error in the share price recorded in the contract?

Murabaha sale is a sale for the capital amount with a known profit, and it is stipulated that the buyer must be aware of the capital amount. If the bank makes a mistake in the capital amount and then clarifies it, you have the right to claim against it for the error and the corresponding profit. If the capital amount was less than what was initially stated, the sale is valid, and the buyer has the right to claim against the seller for the excess amount and its share of the profit. It is not permissible for the bank to pay you the price difference without deducting the corresponding profit, because that leads to usury (riba). Either the bank waives the profit corresponding to the excess and leaves it for you, or you return the excess and the bank waives the corresponding profit from the debt.