What is the ruling on purchasing an item at a price higher than its original price due to the seller's anger at the buyer for changing the type of item after the packaging process had begun?

If the seller increases the price of the sold item to your brother beyond its usual price, this is permissible and not forbidden. As long as the sale was concluded with mutual consent, it is valid and there is no issue with it. There is nothing wrong with your brother buying the item at the mentioned price, and he is not obligated to anything further.