This combination picture shows some revellers wearing masks while dressed as “Botargas” during carnival celebrations in Almiruete, Spain, February 25, 2017. (Photo by Sergio Perez/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 Lebanese man carries an injured woman away from the site of a car bomb explosion in a Shiite area and stronghold of the Lebanese militant group Hezbollah at the southern suburb of Beirut, Thursday January 2, 2014. A large explosion has rocked a stronghold of the Shiite Hezbollah group in the southern suburbs of the Lebanese capital. (Photo by Hussein Malla/AP Photo)

A member of the pro-government “red shirt” movement attacks a Buddhist monk outside the National Anti-Corruption Commission office in Nonthaburi province, on the outskirts of Bangkok March 24, 2014. Members of the movement attacked the monk after he shouted complaints to the group blocking a road near the National Anti-Corruption Commission. (Photo by Chaiwat Subprasom/Reuters)

Yakelin Hernandez, 18, poses for a photograph near The Malecon where The Carnival was held, on August 14, 2015. Colorful costumes, dancing, parades and street parties on the Malecon in Havana, Cuba are all part of Havana Carnival 2015 which was held in August. (Photo by Sarah L. Voisin/The Washington Post)

Athletes from Australia's Olympic team going to the 2016 Olympics in Rio present their uniforms alongside Brazilian Samba dancer Sashya Jay at an official unveiling ceremony at Sydney's Bondi Beach, March 30, 2016. (Photo by Jason Reed/Reuters)

A reveler in costume laughs during the “Cordao do Boitata” street party in Rio de Janeiro, Brazil, Sunday, February 24, 2019, one of the many parades before the official start of Carnival on March 1. (Photo by Leo Correa/AP Photo)

A zookeeper wearing orangutan costume tries to escape while zookeepers hold up a net in an attempt to capture it during an Escaped Animal Drill at Tama Zoological Park in Tokyo, Japan on February 22, 2019. The annual escape drill is held to train zookeepers what to do in the event of an animal escape. This year a member of staff wearing an orangutan costume was captured and subdued with large nets, sticks and tranquilizer guns to make sure the orangutan did not get away. (Photo by Rodrigo Reyes Marin/ZUMA Wire/Alamy Live News)