Members of the Hitler Youth who are trained to report airstrikes repaining their bicycles. Published by: “Die Sirene”. 1942. (Photo by Herbert Hoffmann/Ullstein Bild via Getty Images)

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.

Two styles of cleaned bird's nest, Yan Zhan (L) and Su Zhan (R) await repacking at a processing plant in Kuala Lumpur, February 17, 2015. Prized in China for is alleged health benefits for hundreds of years, nests made from swiftlets' saliva are being mixed into coffee and cereal as the Southeast Asian producers of the delicacy seek to broaden its appeal, and their profit margins. The nests are among the world's most expensive foods, selling for up to $2,500 a kg and the swiftlets that weave them are indigenous to Indonesia, Malaysia, Thailand and Vietnam. (Photo by Olivia Harris/Reuters)

In this photo taken Tuesday, June 23, 2015, a Ukrainian serviceman from the Kiev-2 volunteer battalion fires an weapon at a frontline in the village of Krymske, east Ukraine. Few places along the front line in east Ukraine see regular fighting as bitter as the village of Krymske. For now, Krymske is in the hands of Ukrainian government forces and the volunteer battalions that fight alongside them. (Photo by Evgeniy Maloletka/AP Photo)

Josef Stalin's head is left in a Budapest street after a statue to the communist dictator was torn from its plinth during the Hungarian Revolution in 1956. (Photo by Robert Hofbauer/Radio Free Europe/Radio Liberty)

Listed as endangered on the IUCN red list of threatened species, a humphead wrasse, or Napoleon fish, swims in an aquarium during an event in Tokyo's shopping district of Ginza on August 5, 2019. (Photo by Kazuhiro Nogi/AFP Photo)

Filipino students performs during the parade at the 125th Philippine’s Independence Day at Dubai World Trade Centre on June 10, 2023. (Photo by Leslie Pableo for The National)

Women in Chicago being arrested for wearing one piece bathing suits, without the required leg coverings. (Photo by Topical Press Agency/Getty Images). 1922