'The popcorn will come at a cost', 'The popcorn isn't free', 'The popcorn Expense $10', 'You will need to pay for the popcorn' or, simply, 'The popcorn is just not free'. The assertion, 'You usually takes your baby within the flight free of charge' would be in opposition to 'You should pay back to take your infant on the plane' or 'It is not free',