Fees charged by ridesharing companies like Uber and Lyft are boosting their financial fortunes, according to a report in The Wall Street Journal, which places special emphasis on fees for reserving a ride. The reporter said she was charged a reservation fee of $19.31 for an Uber ride to the airport in Phoenix. That was on top of a $7.61 booking fee, a $4.75 airport surcharge and the $23.39 fare. The story noted that Uber just reported its first annual profit and Lyft has trimmed its losses.

Some of the ride-hailing fees, like government-mandated airport, venue and congestion surcharges, are outside the companies’ control, the article said. But Lyft and Uber set others, and they vary widely by trip. Riders get few, if any, details up front, The Wall Street Journal said. Both apps display only the total price when passengers are booking or reserving a ride, and both companies say what’s most important is that passengers know the final price up front.

An Uber spokesperson told the WSJ the option to reserve a ride gives travelers “peace of mind.”A Lyft spokesperson told the WSJ: “Travelers pay a little extra to have a driver accept your ride in advance and get to your pickup location on time, while also locking in the price in case, for example, it’s raining and there is a surge in demand.”

Uber CEO Dara Khosrowshahi has said Uber Reserve is aimed at high-income consumers who can pay more for “higher reliability,” according to the WSJ article. And it’s working, he said in a recent presentation. Now 20% of its airport pickups are from reserved rides. But Uber has also seen strong demand outside travel, especially in the suburbs, he said.