A woman is helped out of the wrecked car of a train that derailed at the station of Pioltello Limito, on the outskirts of Milan, Italy, Thursday, January 25, 2018. Italian officials said that the commuter train derailed in northern Italy, killing some people, seriously injuring 10 and trapping others heading into Milan at the start of the work day. (Photo by AP Photo/Stringer)

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.

Crocodile meat parts stands on display on Huangsha Seafood Market in Guangzhou, Guandong Province, China, 20 January 2018. Tsukiji Market of China or Huangsha Seafood Market is biggest one in Southern China and one of the biggest in China, as there are literally hundreds of different varieties of fish and seafood scattered throughout the market. (Photo by Aleksandar Plavevski/EPA/EFE)

A member of the “Bloco Ultima Hora” group gets off a boat during Carnival of the Waters, where costumed and colorful boats navigate the river Tentem, around the islands near the city of Cameta, Brazil on February 8, 2018. (Photo by Ueslei Marcelino/Reuters)

Actress Hayley Hasselhoff leads models, diversity campaigners and social media influencers question the lack of curves in the female fashion industry outside 180 The Strand on February 16, 2018 in London, England. (Photo by Neil P. Mockford/Getty Images)

Brides display their hands decorated with henna around a bride as she poses for her own photographer during a mass marriage ceremony in which, according to its organizers, 70 Muslim couples took their wedding vows, in Ahmedabad, India, February 11, 2018. (Photo by Amit Dave/Reuters)

People react as a Canadian man wearing only a pair of shorts orders a drink from a fast food outlet in Gangneung Curling Centre on day 10 of the PyeongChang 2018 Winter Olympic Games on February 19, 2018 in Gangneung, South Korea. (Photo by Carl Court/Getty Images)

Russia' s Tiffani Zagorski and Russia' s Jonathan Guerreiro compete in the ice dance free dance of the figure skating event during the Pyeongchang 2018 Winter Olympic Games at the Gangneung Ice Arena in Gangneung on February 20, 2018. (Photo by Lucy Nicholson/Reuters)