Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.

Finding just the right spot above the clouds at Camp 1 on Ama Dablam, Danuru Sherpa uses his iPhone to catch up with friends and family. Even at 18,500 feet (5,654 meters), climbers here can check their email and other dispatches from the world below. (Photo by Aaron Huey/National Geographic)

A boy rides on a snow wagon towed by a robot dressed as a Teddy bear, which only moves forward by moving its legs, during the Ice and snow carnival at Taoranting park in Beijing February 9, 2015. (Photo by Kim Kyung-Hoon/Reuters)

Afghan National Army (ANA) soldiers sit waiting to return their weapons after a day of traning at the Kabul Military Training Center (KMTC) October 3, 2010 in Kabul, Afghanistan. There are between 5,000 to 7,000 troops on the training facility in eight-week cycles trained by the coalition forces to ultimately take over the role of military operations in the country. (Photo by Paula Bronstein/Getty Images)

Face Off is an American reality television game show on the Syfy cable network in which a group of prosthetic makeup artists compete against each other to create prostheses such as those found in science fiction and horror films.

Afghan boys ride on donkey cart transporting plastic bottles for recycling, on the outskirts of Kabul, Afghanistan, on 16 September 2020. Nearly 19 years after the fall of the Taliban regime and the United States invasion, the Afghan government and insurgents on 12 September, began peace negotiations in Doha. (Photo by Hedayatullah Amid/EPA/EFE)

Carnival participants dressed in costume and wearing body paint pose for a group picture during the annual Zambo carnival held in Lebanon's northern city of Tripoli on March 14, 2021, marking the last period of excess on the eve of the Christian Greek Orthodox lent. The inspiration of the annual Zambo celebration is unclear, despite it being a tradition that stretches back over a century to when an emigrant to Brazil returned to his native Tripoli bringing the carnival with him. (Photo by Ibrahim Chalhoub/AFP Photo)

A health worker administers a dose of the Sinovac COVID-19 vaccine to a worker in a local entertainment venue area where a new cluster of COVID-19 infections were found in Bangkok, Thailand, Wednesday, April 7, 2021. Officials in Thailand’s capital have ordered a two-week closure of all entertainment venues in three districts to try to limit the spread of the coronavirus from nightspots there. (Photo by Sakchai Lalit/AP Photo)