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 man looks inside an overturned truck after an accident along the road between Nouahibou and Nouakchott, Mauritania December 3, 2009. (Photo by Rafael Marchante/Reuters)

“Spare bits = spare bots. Time on hands + obsession with uselessness = make trivial things. Made from capacitors, diodes, resistors, leds, bits of wire, solder, and time...” – Lenny & Meriel. Photo: “9V tragedy”. (Photo by Lenny&Meriel)

A woman wearing cut-off jeans and a halter-neck sun top in St Tropez, 1972. (Photo by Roy Jones)

British reality stars Kerry Katona and Michelle Heaton Relax poolside with their families in Bridgwater, Somerset, England on August 30, 2016. Kerry Katona was wearing a “Swag” t-shirt before stripping down to a red bikini. Kerry looked to be having a great time with Michelle and family. (Photo by FameFlynet UK)

A villager pours pesticide from a bucket as Mount Sinabung spews ash at Kebayaken village in Karo district, Indonesia's North Sumatra province, on December 4, 2013. The country has ordered the evacuation of 15,000 residents near the active volcano. (Photo by Roni Bintang/Reuters)

Smithfield meat porters march on the Home Office, bearing a petition which calls for an end to all immigration into Britain, 25th August 1972. (Photo by Keystone/Hulton Archive/Getty Images)

An Afghan judge hits a woman with a whip in front of a crowd in Ghor province, Afghanistan August 31, 2015. An Afghan man and woman found guilty of adultery received 100 lashes on Monday in front of a crowd who filmed their punishment, TV footage showed. (Photo by Reuters/Pajhwok News Agency)