People walk down the street while Hurricane Matthew approaches in Port-au-Prince, Haiti October 3, 2016. (Photo by Carlos Garcia Rawlins/Reuters)

A Snowboarder participates in a waterslide contest, which consists of gliding over a water pool embedded in snow, during the closing event of the ski resort of Nendaz, southwestern Switzerland, Monday, April 21, 2014. (Photo by Maxime Schmid/AP Photo/Keystone)

Nasoin Akhter, 15, has her makeup done at a beauty parlor on the day of her wedding to a 32-year-old man, August 20, 2015, in Manikganj, Bangladesh. In June of this year, Human Rights Watch released a damning report about child marriage in Bangladesh. The country has one of the highest rates of child marriage in the world, with 29% of girls marrying before the age of 15, and 65% of girls marrying before they turn 18. (Photo by Allison Joyce/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 Bulgarian tourists pose in front of the Eiffel Tower in Paris on their last day in the capital on March 24, 2014. (Photo by Franck Fife/AFP Photo)

A woman directs traffic in the pouring rain in Pyongyang, North Korea on May 3, 2016. The city is preparing for the Workers' Party Congress starting on May 6th. It will be the first time since 1980 that the ruling party has convened. (Photo by Linda Davidson/The Washington Post)

People take cover outside the Fort Lauderdale-Hollywood International airport after a shooting took place near the baggage claim on January 6, 2017 in Fort Lauderdale, Florida. Officials are reporting that five people were killed and 8 wounded in an attack by a single gunman. (Photo by Joe Raedle/Getty Images)

People sit at an oversize picnic table in Soho Square in London May 19, 2014. (Photo by Luke MacGregor/Reuters)