A model wears a floral head dress as she promotes a chain of garden centres at the Royal Horticultural Soceity's Chelsea Flower Show in London, Britain, May 18, 2015. (Photo by Toby Melville/Reuters)

Participants re-enact the “Battle of Five Armies” from J.R.R. Tolkien's novel “The Hobbit” in a forest near the town of Doksy, Czech Republic June 6, 2015. According to event organizers, hundreds of enthusiasts dressed as characters such as elves, dwarves, goblins and orcs from the book “The Hobbit” re-enacted the clash. (Photo by David W. Cerny/Reuters)

A man fires a weapon as he dances during a traditional excursion near the western Saudi city of Taif, August 8, 2015. Saudis usually party in such excursions as they celebrate weddings or graduations. (Photo by Mohamed Al Hwaity/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.

Revellers celebrate during the “Bloco da Lama”, a mud carnival, in Paraty, Brazil, on February 10, 2018. “Bloco da Lama” started in 1986 by teenagers playing with mud and became a traditional event at the historical city of Paraty. (Photo by Mauro Pimentel/AFP Photo)

A woman dances as people gather near EU headquarters during a so called “European Demonstration for Freedom and Democracy” protest against COVID-19 security measures taken by European governments, in Brussels, Saturday, May 29, 2021. (Photo by Olivier Matthys/AP Photo)

A demonstrator takes part during a rally against Chile's government on the second anniversary of the protests and riots that rocked the capital in 2019, in Santiago, Chile, October 18, 2021. (Photo by Ivan Alvarado/Reuters)

A participant in costume and make-up poses for a photo during a Halloween parade at Walibi park in Wavre, Belgium, October 31, 2018. (Photo by Yves Herman/Reuters)