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.

In this Saturday, March 21, 2015 photo, a porter rests carrying supplies for the upcoming climbing season, near the Everest Base camp, Nepal. Nepal has cleared more than 300 mountaineers to climb Mount Everest after they had to abandon last year's efforts when an ice avalanche killed 16 guides in the mountain's deadliest disaster, an official said on March 20. The three-month climbing season for Everest, the world's tallest mountain, begins in March. (Photo by Tashi Sherpa/AP Photo)

Initially the project started when I was working in Atlanta. About four years ago, a roommate of mine had a Yorkie and we thought it would be funny to take some photos of this really cute dog with a few handguns. Once my friends saw the photos they started asking me to take pictures of their dogs with other firearms... (Photo and caption by Ben Haulenbeek/Puppies with guns calendar 2015)

Vast collection of fine art photography about to open at Pier 24 in Manhattan. One of the world's most prestigious annual photography events, The Photography Show is the longest-running and foremost exhibition dedicated to the photographic medium, offering a wide range of museum-quality work, including contemporary, modern, and 19th-century photographs as well as photo-based art, video, and new media. Here: Les Trois Femmes Deux, 2018. (Photo by Mickalene Thomas/Courtesy of Yancey Richardson Gallery, New York)

A man fires a weapon as he dances during a traditional excursion near the western Saudi city of Taif, August 8, 2015. Saudis usually party in such excursions as they celebrate weddings or graduations. (Photo by Mohamed Al Hwaity/Reuters)

Handguns turned in from the public as part of the “Gun Turn-in” event where a $100 gift card is given for every firearm and a $10 gift card for each BB-gun, air-gun, or replica firearm turned over to police at Universal Missionary Baptist Church in Chicago, Illinois, U.S. May 28, 2016. (Photo by Jim Young/Reuters)

Guns decorated with gold and jewellery are displayed in the Drugs Museum, used by the military to showcase to soldiers the lifestyles of Mexican drug lords, at the headquarters of the Ministry of Defense in Mexico City, October 14, 2016. (Photo by Henry Romero/Reuters)