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.

Actresses Vonnie Lui (R) and Yukiku Suou (L) attend the “3D s*x And Zen: Extreme Ecstacy” photocall at the Majestic Beach Pier during the 64th Cannes Film Festival on May 14, 2011 in Cannes, France. (Photo by Michael Buckner/Getty Images)

“Jessica”, a silicon sеx doll for sexual encounters lies on a bed at the “Bordoll” brothel on April 17, 2019 in Dortmund, Germany. Bordoll is Germany's first brothel to specialize in sеx dolls. It currently offers 13 female dolls and one male doll and will soon be expanding its female line-up. Schwarz says “sеx dolls are so popular because the client can do what he wants to and nobody complains”. (Photo by Lukas Schulze/Bongarts/Getty Images)

Li Tingting, second from right, laughs as she is lifted off the ground by her wife Teresa Xu, right, outside of a beauty salon where the two were preparing for their wedding as clerks from an adjacent shop look on in Beijing, Thursday, July 2, 2015. Li, a 25-year-old prominent women's rights activist who was released from detention in April, held the wedding ceremony with her partner Teresa on Thursday and announced their marriage in an effort to push for LGBT (lesbian, gay, bisexual, and transgender) rights in China. (Photo by Mark Schiefelbein/AP Photo)

These are some of the Real Doll bodies made by Abyss Creations being assembled in the factory on Tuesday, September 12, 2017 in San Marcos, California. Customers can dictate their partner’s character by choosing between 18 personality traits including shy, sensual, jealous, moody or talkative. (Photo by Eduardo Contreras/San Diego Union-Tribune via ZUMA/Rex Features/Shutterstock)

An exotic model poses for photographs at a news conference to promote the “Expo Sеx and Eroticism” adult exhibition in Mexico City, Mexico March 1, 2017. (Photo by Carlos Jasso/Reuters)

Children exercise before a wrestling practice session at an old Basque ball game gymnasium in downtown Havana, October 30, 2014. (Photo by Alexandre Meneghini/Reuters)

A Tai Yai boy waits for a ceremony to begin at Wat Don Chedi on April 7, 2014 in Mae Hong Son, Thailand. Poy Sang Long is a Buddhist novice ordination ceremony of the Shan people or Tai Yai, an ethnic group of Shan State in Myanmar and northern Thailand. Young boys aged between 7 and 14 are ordained as novices to learn the Buddhist doctrines. It's believed that they will gain merit for their parents by ordaining. (Photo by Taylor Weidman/Getty Images)