'The popcorn will come at a cost', 'The popcorn isn't free', 'The popcorn cost $10', 'You must pay for the popcorn' or, merely, 'The popcorn is not free'. The assertion, 'You will take your child within the flight free of demand' can be in opposition to 'You should pay out to choose your infant on the plane' or 'It's not free', or informally, 'You