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 woman smokes marijuana during the annual 4/20 marijuana rally on Parliament Hill in Ottawa, Ontario, Canada, April 20, 2017. (Photo by Chris Wattie/Reuters)

Two men try to load their just purchased Samsung 55" TV into a car, at a Best Buy store in Fairfax, Virginia on November 26, 2015, on a Black Friday sale that started a day earlier during Thanksgiving evening. The US holiday shopping season kicks off with "Black Friday" – the day after the Thanksgiving holiday – with a frenzy expected at stores around the country as retailers slash prices. (Photo by Paul J. Richards/AFP Photo)

A girl jumps over a campfire while celebrating Ivan Kupala Night, a traditional Slavic holiday not far from Kiev on July 6, 2013. During the celebration, originating in pagan times, people plait wreaths, jump over fires, and swim naked. (Photo by Sergei Supinsky/AFP Photo)

A monkey is led by its trainer Qi Defang during training for a circus in Suzhou, Anhui province, November 29, 2014. Suzhou is known as the hometown of circus troupes in China and has more than 300 circus troupes. (Photo by William Hong/Reuters)

Dancers from the British theater company Motionhouse perform a show with excavators entitled “Traction” on the Prado beach in Marseille, France, on May 10, 2013. (Photo by Boris Horvat/AFP Photo)

Crews move a 39 foot long, 16 foot tall, 2400 lbs. replica of a Tyrannosaurus Rex from behind the Museum Of Science And History in Jacksonville, Fla., to its new location in front of the entrance of the museum Wednesday morning, May 20, 2015, to kickoff the upcoming Dinosaurs Unearthed exhibit. The exhibiti, which opens this week, includes animatronic dinosaurs as well as prehistoric fossils and runs through September 7. (Photo by Bob Self/The Florida Times-Union via AP Photo)

A little girl takes a picture of a lion in the zoo in Frankfurt, Germany, Tuesday, September 13, 2016. (Photo by Michael Probst/AP Photo)