The cost of airport food is soaring.

Travelers passing through airports tend to expect to pay more for basic items such as water bottles — but why is it so much more expensive?

A reporter for USA Today shared in a column that she purchased a 24-ounce flip-top bottle of Smartwater and a snack-sized bag of Snyder’s of Hanover Mini Pretzels for a total of $9.47 at a Hudson News at John F. Kennedy International Airport. The water bottle cost $4.99 and the pretzels cost $3.99.

In comparison, the 7-11 in her neighborhood in Queens sold the same water bottle for $3.29 and the pretzel options ranged from $1.69 for store brand to $3.69, though they didn’t have the exact pretzels she bought at JFK Airport.

Rules regarding pricing vary from airport to airport, and there are no national regulations for how airport vendors set their prices, but overall, many airports mark up their prices to counterbalance other costs.

“To offset higher operational costs, many airports add a 10% to 15% margin on local street prices, reflecting the higher costs of operating in secure, high-traffic environments,” the Port Authority told USA Today in a statement.

Operational costs include higher rent, security, utilities and staffing, which is more complex and expensive than at smaller airports of off-airport properties, as well as guaranteed cost-of-living increases for its on-property minimum wage workers, the agency explained.