Indian Air Force soldiers toss their rifles as they perform during the full-dress rehearsal for Indian Air Force Day at the Hindon air force station on the outskirts of New Delhi October 6, 2015. (Photo by Anindito Mukherjee/Reuters)

A commuter gestures to Boris Johnson as he rides across Vauxhall Bridge in London, England on November 19, 2015. The London mayor was opening a cycle superhighway. (Photo by John Stillwell/PA Wire)

An Israeli woman scrambles through the mud and under barbed wire at the competition of the Legion Run in the Menara Cliffs area of Kiryat Shmona, in northern Israel, near the Lebanon border 14 October 2016. Hundreds of participants ran five kilometers cross country in steep terrain and then navigated various obstacle courses including steep inclines and mud holes. It is the first time this non-competitive but supportive sporting event is held in Israel. (Photo by Jim Hollander/EPA)

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.

Competitors take part in the 8th annual World Gravy Wrestling Championships at the Rose n Bowl Pub in Bacup, north west England on August 31, 2015. Contestants must participate in fancy dress and wrestle in a pool of Lancashire Gravy for 2 minutes whilst being scored for a variety of wrestling moves. (Photo by Oli Scarff/AFP Photo)

Students exercise in body training at Bishan Vocational Education Center in Chongqing, southwest China, January 13, 2016. These students were trained to be stewardesses of the high-speed train. (Photo by Xie Jie/Xinhua)

People carry drinks at 80s Bar in Damascus, Syria, March 11, 2016. In Damascus's Old City, just a mile from the battered frontline between government and rebel-held territory, young Syrians smoke, drink beer or soft drinks, and talk about anything but the war. The revival of activity in this once-vibrant quarter is part of efforts to project an air of normality in the Syrian capital, even as the five-year-old war that has killed more than 250,000 people and created 5 million refugees continues to rage nearby. (Photo by Omar Sanadiki/Reuters)

These are the stomach-churning pictures of the swing at the end of the world – a rickety wooden swing hanging over a precipice 2,660 metres above sea level – and not a seatbelt in sight. (Photo by Caters News)