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.

Armed Syrian Turkmen villagers are seen near the northern Syrian village of Yamadi, near the Turkish-Syrian border, Syria, November 24, 2015. Turkey shot down a Russian warplane near the Syrian border on Tuesday saying it had repeatedly violated its air space, one of the most serious publicly acknowledged clashes between a NATO member country and Russia for half a century. (Photo by Reuters/Stringer)

This artist's scoreboard displays a fictional game between Mars and Earth, with Mars in the lead. It refers to the success rate of sending missions to Mars, both as orbiters and landers. Of the previous 39 missions targeted for Mars from around the world, 15 have been successes and 24 failures. For baseball fans, that's a batting average of .385. The United States has had 13 successes out of 18 attempts, or a “batting average” of .722. NASA's Curiosity rover, set to land on the Red Planet the evening of Aug. 5, 2012 PDT (morning of Aug. 6 EDT), will mark the United States' 19th attempt to tackle the challenge of Mars, and the world's 40th attempt. (Image by NASA/JPL-Caltech)

Robert Price of TREWGrip LLC demonstrates a TREWGrip handheld rear-type keyboard and air mouse for Apple and Android tablets at the “CES: Unveiled”, media preview for International CES, at the Mandalay Bay Convention Center in Las Vegas on January 5, 2014. (Photo by Robyn Beck/AFP Photo)

Artist Joe Hill poses on his 3D artwork, from the “Joe and Max” project as part of an advertising campaign, during its presentation at a park in Moscow, Russia, July 4, 2015. (Photo by Sergei Karpukhin/Reuters)

Peruvian shamans holding a figure of a Nino Jesus (Child Jesus) and a snake perform a ritual at the Rimac river to fight the negative effects of the Nino weather phenomena over Nature, in Lima, October 1, 2015. (Photo by Mariana Bazo/Reuters)

A photo provided by the Atlanta Journal-Constitution shows Atlanta police officer T. R. Coxe removing painted material of a large swastika featuring a likeness of Republican presidential candidate, Donald Trump, along the northbound Buford Highway Connector just south of the Piedmont exit, in Atlanta, Georgia, USA, 09 December 2015. Just days after Donald Trump's call to ban Muslims from entering the United States, someone painted large swastikas featuring the Republican presidential candidate's face on at least two northeast Atlanta bridge supports. The symbol, which includes a cartoon of Trump sporting a Hitler-like mustache, was painted along the Buford Highway Connector. A second, similar image was found on a concrete bridge support on nearby Piedmont Road. Trump said in a statement released on 07 December that there should be a total and complete shutdown of Muslims entering the United States. (Photo by John Spink/EPA/AJC)

Chinelos (traditional costumed dancers) perform in front of San Andres Ocotlan church as part of continuing festivities to welcome the new year in Calimaya, Mexico on January 4, 2016. (Photo by Arturo Hernandez/Demotix/Corbis)