Because many hotels don’t include these fees in the prices they advertise, they can come as a surprise to consumers when they check in or even when they are settling up at the end of their stay.

The amount of revenue the hotel industry rakes in from resort and other fees and surcharges is huge: $2.9 billion in 2018, according to Bjorn Hanson, a hospitality industry consultant in New York.

Booking.com and Expedia are also pressuring hotels to be more upfront about resort fees, even though their motivation may be as much about their bottom line as helping consumers.

Related: Marriott facing lawsuit over ‘deceptive’ resort fees that allegedly harm consumers