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)

Artist Kong Ning wears a wedding dress made from respirators to highlight concerns about air quality and pollution in Beijing, China on December 1, 2015. (Photo by Luo Xiaoguang/Xinhua Press/Corbis)

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.

A man drives a car loaded with electronic and household appliances the Dbayeh highway, at the northern entrance of Lebanon's capital Beirut, on August 11, 2020, following a huge chemical explosion that devastated large parts of the city. (Photo by Joseph Eid/AFP Photo)

A man wears a protective face mask on a street, amid the spread of the coronavirus disease (COVID-19), in Bangkok, Thailand, August 21, 2020. (Photo by Jorge Silva/Reuters)

Proud Boys and Antifa fight after the “Million MAGA March” from Freedom Plaza to the US Capitol in Washington, DC, United States on December 12, 2020. Rally held to back President Donald Trump's unsubstantiated claims of voter fraud in the US election. (Photo by Tayfun Coskun/Anadolu Agency via Getty Images)

Ukrainian law enforcement officers restrain an activist of women's rights group Femen, who holds a protest outside the presidential administration headquarters while marking the International Day for the Elimination of Violence against Women in Kyiv, Ukraine on November 25, 2020. (Photo by Valentyn Ogirenko/Reuters)

Steve Kent skis through Times Square during a snowstorm, Monday, February 1, 2021, in the Manhattan borough of New York. (Photo by John Minchillo/AP Photo)