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 holy men with a decorative faces and headdresses, taken in Kathmandu, Nepal. Wandering through the cities and forests of Nepal are the holy men, or Sadhus, who have left all materialistic pleasures behind to live a life devoted to God. Their appearances vary from brightly coloured face paints, and decorations, to minimalistic practical clothing, but they all represent the fundamental values and meanings of Hinduism. Danish photographer Jan Moeller Hansen visited the ancient capital city of Kathmandu between 2013 and 2016 and documented the mysterious holy wanderers. (Photo by Jan Moeller Hansen/Barcroft Images)

People walk on a sightseeing platform in Zhangjiajie, Hunan Province, China, August 1, 2016. China has opened a 100-metre-long glass skywalk stretching around a cliff on the side of the Tianmen Mountain. The skywalk provides a view of a 300-metre drop and overlooks Tongtian Avenue, a mountain road with 99 turns that snakes up the mountain. When translated in English, it means “Avenue to the Sky”. (Photo by Reuters/Stringer)

Ukrainian artist Dariya Marchenko works on a portrait of Russian President Vladimir Putin named “The Face of War” which is made out of 5,000 cartridges brought from the frontline in eastern Ukraine, in Kiev, July 23, 2015. The portrait will be presented along with a novel which will tell personal stories of six people involved in this project including Daria's own story and stories of people who helped her to collect shells from the frontline. Daria Marchenko calls her art approach philosophic symbolism where every element has its hidden meaning. In her works cartridges mean human's life that was brutally ended. (Photo by Gleb Garanich/Reuters)

Salar de Uyuni (or Salar de Tunupa) is the world's largest salt flat at 10,582 square kilometers (4,086 sq mi). It is located in the Potosí and Oruro departments in southwest Bolivia, near the crest of the Andes, and is elevated 3,656 meters (11,995 ft) above mean sea level. The Salar was formed as a result of transformations between several prehistoric lakes. It is covered by a few meters of salt crust, which has an extraordinary flatness with the average altitude variations within one meter over the entire area of the Salar.

Heavy equipment works along the still under construction Bamiyan-Yakawlang road June 10, 2011 in Yakawlang, Afghanistan. The 69 Million US$ project is supported by the Government of Japan and World Bank. The 90K road project was started three years ago and is slated to be finished within another year. This new road means faster travel from Bamiyan to Afghanistan's only national park, Band-e-Amir. This is in of the safest parts of the country and the hope is to expand tourism in the region. (Photo by Paula Bronstein/Getty Images)

Chocolate is the greatest gift the Earth has given us. The dessert table would be a sad sight without it. It’s so beloved, so appreciated, that the Swedish scientist who named the cocoa plant that gives us chocolate called it Theobroma cacao, which means “food of the gods”. Here: Farmer holding a freshly cut cocoa bean pod, revealing the pulp and seed inside on a rainforest farm. (Photo by Doug McKinlay/Getty Images)