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 guest poses with a magic wand during a soft opening and media tour of “The Wizarding World of Harry Potter” theme park at the Universal Studios Hollywood in Los Angeles, California in this picture taken March 22, 2016. (Photo by Kevork Djansezian/Reuters)

Attendees at Wizard World Comic Con walk through hallways in Chicago, Illinois, United States, August 22, 2015. (Photo by Jim Young/Reuters)

A motorcyclist dodges in the annual water-splashing festival to mark the New Year of the Dai minority in Menglian, Yunnan province April 13, 2015. (Photo by Wong Campion/Reuters)

Engineer Mikhail Venin works on an antenna for the Express AM8 new generation geostationary telecommunications heavy satellite at the large-sized transformed mechanical systems centre of the Reshetnev Information Satellite Systems company in the Siberian town of Zheleznogorsk April 2, 2014. The Express AM6 is a new generation satellite providing services including Russian governmental and presidential mobile communication, digital television and broadcasting, according to the Reshetnev company representatives. (Photo by Ilya Naymushin/Reuters)

Unwanted phones recreated as interactive birds, part of “Escape III” by Anthony Goh and Neil Mendoza seen on display at the Barbican's Digital Revolution exhibition on July 2, 2014 in London, England. The exhibition brings together artists, designers, film makers, musicians and architects who push the boundaries of creativity that digitial technology can offer, and runs from July 3 until September 14, 2014. (Photo by Matthew Lloyd/Getty Images for Barbican Art Gallery)