Libyan rebel soldiers watch as they fire rockets (background) toward Libyan government troops near front-line positions April 6, 2011 outside of Brega, Libya. Rebel militias fighting against Libyan government loyalist soldiers continued their stand-off in the eastern Libyan desert today, regaining ground toward a key oil port while awaiting further NATO airstrikes in their quest to unseat longtime Libyan ruler Muammar Gaddafi. (Photo by Chris Hondros/Getty Images)

Burning Man 2013. The federal government issued a permit for 68,000 people from all over the world to gather at the sold out festival, which is celebrating its 27th year, to spend a week in the remote desert cut off from much of the outside world to experience art, music and the unique community that develops. (Photo by Neil Girling)

Workers work inside a new Antonov airplane at the Antonov aircraft plant in Kiev, Ukraine, September 7, 2015. State-run aircraft maker Antonov built more than 22,000 units of more than one hundred types and modifications of passenger, transport and special-purpose aircraft, including the world's biggest cargo plane Antonov-225 (Mriya), according to the company's official website. (Photo by Gleb Garanich/Reuters)

“The Antonov An-124 Ruslan (NATO reporting name: Condor) is a strategic airlift jet aircraft. It was designed by the Soviet Union's Antonov design bureau. It is the world's largest ever serially-manufactured cargo airplane and world's second largest operating cargo aircraft. During development it was known as Izdeliye 400 in house, and An-40 in the West. First flown in 1982, civil certification was issued on 30 December 1992”. – Wikipedia

Photo: The new metro called “Bombardier MOVIA” with 22,50 meters long and 3,2 meters wide is load on a Antonow An-124 plane for transport to India on February 25, 2009 in Parchim, Germany. (Photo Handout Bombardier Transportation via Getty Images)

Artist Princess Tarinan von Anhalt throws paint into the flow of air coming from the engine of Flexjet’s Learjet 40 XR engine to create a painting on a canvas at Signature Flight Support in West Palm Beach, Florida. The artist associated with the Jet Art Group used the help of Flexjet and their plane to spray paint on a canvas to create distinctive paintings to celebrate the 50th anniversary of Learjet. (Photo by Thomas Cordy/The Palm Beach Post)

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.

The Solar Impulse 2 airplane, flown by test pilot Markus Scherdel, flies off the coast of Oahu during a test flight from Kalaealoa Airfield in Kapolei, Hawaii, March 3, 2016. The solar-powered plane is ready to continue its revolutionary voyage around the world. After the craft was grounded in Hawaii last July due to overheated batteries, it was repaired and upgraded, and a recent initial test flight proved successful. (Photo by Eugene Tanner/Reuters)