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.

The first autonomous and electric shuttle of PostAuto Schweiz in the old village of Sion, Switzerland, June 2016. (Photo by Ruben Sprich/Reuters)

The anthropometric record card of Sarah Giles, a servant who was convicted of stealing in 1897, on display making up part of a mosaic of cards on a table top during a press preview for the Crime Museum Uncovered exhibition at the Museum of London in the City of London, Wednesday, October 7, 2015. Drawn from Scotland Yard's private collection, the show charts more than a century of violence and suffering, from the murders of Jack the Ripper to IRA and al-Qaida bombings. But it also celebrates the brains, bravery and scientific advances that helped catch perpetrators and solve crimes. (Photo by Alastair Grant/AP Photo)

A Nepalese Hindu devotee dresses as a deity as he prepares to participate in festivities at the Shikali Temple during celebrations for the Shikali Jatra festival in the village of Khokana, on the outskirts of Kathmandu, on October 19, 2015. Local villagers, who normally do not celebrate the country's most famous festival of Dashain, celebrate the Shikali Jatra each year. (Photo by Prakash Mathema/AFP Photo)

“The Family of Man” opened at The Museum of Modern Art in January 1955 and was curated by Edward Steichen. It was groundbreaking in its scope – 503 images by 273 photographers from 68 countries – as well as in the numbers of people who experienced it on its tour through 88 venues in 37 countries. The touring exhibit drew over 9 million people and the accompanying catalog sold over 2.5 million copies. Here: “Coney Island, New York”, by American photographer Garry Winogrand, circa 1952. (Photo by Garry Winogrand)

A Hindu devotee wearing a t-shirt printed with a portrait of Lord Shiva takes a holy dip while participating in the “Bol Bom” pilgrimage in Kathmandu August 10, 2015. The faithful, chanting the name of Lord Shiva, run about 15 km (9 miles) barefooted toward Pashupatinath temple seeking good health, wealth and happiness. (Photo by Navesh Chitrakar/Reuters)

Palestinian girl Manar Al-Shinbari (R), 15, who lost her both legs by what medics said was Israeli shelling at a UN-run school where she was taking refuge during the 50-day war last summer, is helped by her sister to put on her headscarf in an apartment in Jabaliya refugee camp in the northern Gaza Strip January 13, 2015. Manar's mother and three of her brothers were killed in the same incident. The girl's family house was destroyed by Israeli shelling during the war. (Photo by Mohammed Salem/Reuters)

People ride a prototype of a driverless vehicle as it is moves through a pedestrian area in Greenwich, east London, February 11, 2015. Britain has begun testing driverless cars in four cities, launching the first official trials ahead of a series of planned rule reviews to accommodate the new technology. (Photo by Suzanne Plunkett/Reuters)