Ana Ivanovic of Serbia plays a backhand return to Maria Sharapova of Russia during their women's singles final match at the Brisbane International tennis tournament in Brisbane, January 10, 2015. (Photo by Jason Reed/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.

Attnedees dressed in Zombie outfits walk down the Gaslamp Quarter outside of the 2015 Comic-Con International in San Diego, California July 8, 2015. (Photo by Sandy Huffaker/Reuters)

Men ride a scooter through a flooded street after heavy rains in New Delhi, India, August 6, 2019. (Photo by Adnan Abidi/Reuters)

Hindu devotees, their cheeks pierced with metal rods, wait to participate in a religious procession during Thaipusam festival in Chennai, India, Tuesday, February 3, 2015. Thaipusam, celebrated in honor of Hindu god Lord Murugan, is an annual procession by Hindu devotees seeking blessings, fulfilling vows and offering thanks. (Photo by Arun Sankar K./AP Photo)

A wild leopard runs on the stairs as it tries to escape from a compound of a house in Kathmandu, Nepal June 1, 2016. (Photo by Navesh Chitrakar/Reuters)

Children guarded by Hungarian police play on the ground after being detained along with other migrants who illegally crossed from Serbia to Hungary near the village of Asotthalom, Hungary, September 16, 2015. (Photo by Dado Ruvic/Reuters)

Sumo wrestler Kaiho eats a “chanko” meal in Nagoya, Japan on July 18, 2017. After ending practice at 10:30 a.m., the wrestlers mingle with fans, sign autographs and pose for photos before the first of their two daily meals. (Photo by Issei Kato/Reuters)