Greyhounds with stuffed and sprung model monkeys strapped to their backs before a hurdle race at Wellinborough. (Photo by E. Bacon). 21st April 1928

People take pictures of the Tribute in Light while it is illuminated next to the Statue of Liberty (C), One World Trade Center and the Empire State Building during events marking the 14th anniversary of the 9/11 attacks on the World Trade Center in New York September 11, 2015. (Photo by Eduardo Munoz/Reuters)

Jeffrey Shiau, 35, a volunteer from the crowd, spits water into the mouth of Sam Kaufman, 27, a performer from the Human Fountains, during a reopening party held as coronavirus disease (COVID-19) restrictions are gradually lifted in Los Angeles, California, U.S. June 15, 2021. (Photo by Cheney Orr/Reuters)

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 French soldier stands near a military combat command vehicle on display at The Defence and Security Exhibition on September 13, 2011 in London, England. ExCeL London is hosting the exhibition with hundreds of manufacturers from all over the world displaying their hardware. (Photo by Peter Macdiarmid/Getty Images)

Bronn, a Dutch shepherd, launches 22 feet, 6 inches, during the Dock Dogs Outdoor Big Air for the GoPro Mountain Games, Thursday, June 9, 2022, at Lionshead Village in Vail, Colo. The big air is always a crowd favorite as dogs can fly nearly 30 feet in distance through the air. (Photo by Chris Dillmann/Vail Daily via AP Photo)

Boeing 747-400 of KLM in approach for the “Princess Juliana” airport, Netherlands Antilles Sint Maarten on July 2, 2002. (Photo by LUPOO/Ullstein Bild via Getty Images)