Mongolian herder, Khurelsukh, throws the carcass of a goat onto a heap as he struggles to deal with losing a quarter of his herd, on March 8, 2010 in Bayantsogt, Tuv province, Mongolia. (Photo by Paula Bronstein /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.

In this Monday, April 27, 2015 photo, a Nepalese man walks over fallen rocks and past a crushed car on the way to Dhunche, Nepal, a village in Langtang National Park, two days after a 7.8-magnatude earthquake hit the region. The photographer, Joe Sieder, said the man was part of a group of Nepalese workers and trekkers who left Syabrubesi earlier that day and hiked about 30 km (19 miles) for 13 hours, mostly over boulder-strewn roads with some small landslides along the way to make their way to a passable road. (Photo by Joe Sieder via AP Photo)

Joshua Patino stands on a ladder to put finishing touches on a giant dinosaur exhibit at PAX East in the Boston Convention and Expo Center, Thursday, April 21, 2016, in Boston. PAX East, an annual celebration of gaming culture, is expected to draw tens of thousands of visitors Friday through Sunday. It's a place where serious gamers can preview unreleased video games and devices, compete in tournaments, hear live music and meet others for whom gaming is a way of life. (Photo by Elise Amendola/AP Photo)

A woman in traditional Malaysian attire welcomes leaders to the official dinner at the venue of the Association of Southeast Asian Nations (ASEAN) Summit in Kuala Lumpur, Malaysia November 21, 2015. (Photo by Jorge Silva/Reuters)

Singer Rihanna prepares for a photoshoot with photographer Annie Leibovitz in Havana, Cuba, May 28, 2015. (Photo by Reuters/Stringer)

Rolando Pujol Rodriguez photographed the Cuban raft exodus in 1994, and twenty years later Enrique de la Osa took portraits of some of the people who made it to the United States, in this story which combines archive and present day images. Here: People put the finishing touches to a makeshift boat on a rooftop before lowering it onto a truck and launching it into the Straits of Florida towards the U.S., on the last day of the 1994 Cuban raft exodus in Havana, in this September 13, 1994 file photo. (Photo by Rolando Pujol Rodriguez/Reuters)

A driver on the Horseshoe Pass in North Wales wiping the snow from the windscreen of his car during a heavy snow storm, 18th January 1937. (Photo by Norman Smith)