Soldiers from 12 Mechanized Brigade perform a simulated casualty evacuation at the Ministry of Defence training area at Copehill Down on Salisbury Plain on March 9, 2012 in Wiltshire, England. The Defence Secretary Philip Hammond visited the military facility to meet soldiers from the Brigade who are shortly to deploy to Afghanistan for Operation Herrick 16, and troops from the 3rd Battalion, the Yorkshire regiment which lost five of the six men who died this week in the deadliest single attack in Afghanistan since 2001. (Photo by Matt Cardy/Getty Images)

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.

Some bats in the forested area of Guapiles, Costa Rica, 21 April 2020. (Photo by Jeffrey Arguedas/EPA/EFE)

Ahmad Sayed Rahman, a five-year-old Afghan boy who lost his right leg when he was hit by a bullet in the crossfire of a battle, dances with his prosthetic leg at the International Committee of the Red Cross (ICRC) hospital for war victims and the disabled, in Kabul on May 7, 2019. (Photo by Wakil Kohsar/AFP Photo)

This photo taken on November 20, 2022 shows a woman wearing the Chinese transitional dress, known as Hanfu, taking part in a parade in Shenyang in China's northeastern Liaoning province. (Photo by AFP Photo/China Stringer Network)

A farmer harvests the lotus roots at a lotus pond in the Lingjiaohu Village of Nanxian County, Yiyang City, Central China's Hunan Province on April 26, 2023. Farmers in Lingjiaohu Village of Nanxian County have recently been busy with harvesting lotus roots. (Photo by Xinhua News Agency/Rex Features/Shutterstock)

A vendor arranges dates on his cart at a market in Rawalpindi on June 1, 2023. (Photo by Farooq Naeem/AFP Photo)

A young girl dressed as living goddess Kumari drinks juice as she waits for Kumari Puja, a worship ritual at Hanuman Dhoka, Basantapur Durbar Square, Kathmandu, Nepal, Wednesday, September 27, 2023. Girls under the age of nine gathered for the tradition of worshiping young prepubescent girls as manifestations of the divine female energy. The ritual holds a strong religious significance in the Newar community that seeks divine blessings to save small girls from diseases and bad luck in the years to come. (Photo by Niranjan Shrestha/AP Photo)