Medics carry an injured at the explosion site in the busy center of Turkish capital, Ankara, Turkey, Sunday, March 13, 2016. The explosion is believed to have been caused by a car bomb that went off close to bus stops. News reports say the large explosion in the capital has caused several deaths and many casualties. (Photo by AP Photo)

An aerial view of a livestock enclosure of the Himba people, in October, 2014, in the Namib Desert, Namibia. A photographer has captured a bird's eye view of the stunning Namib Desert from a paraglider. Theo Allofs travels the world taking stunning pictures of untouched landscapes from a unique perspective. Soaring 300 metres above ground, Theo shot the yellow sand dunes, dry red river beds and remote townships in Namibia. (Photo by Theo Allofs/Barcroft Media)

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.

Ukrainian artists assemble a barbecue grill in the shape of Moscow's Kremlin at their workshop in Kiev May 14, 2015. A group of Ukrainian artists are working on a project entitled “Mordor on Fire” where they create grills that are sold, and some donated to Ukrainian soldiers in the eastern conflict zone. (Photo by Gleb Garanich/Reuters)

A Palestinian student jumps through a fire ring during a military-style show at a school in Rafah in the southern Gaza Strip March 28, 2016. (Photo by Ibraheem Abu Mustafa/Reuters)

Joanne the Scammer (L) and model Amber Rose attend the Amber Rose SlutWalk 2016 at Pershing Square on October 1, 2016 in Los Angeles, California. (Photo by Amanda Edwards/FilmMagic)

A young woman wearing the summer Kimono, “Yukata” watches the goldfishes during the press preview of “Eco Edo Nihombashi Art Aquarium 2014” exhibition in Tokyo on July 10, 2014. The two-month-long goldfish exhibition will starts July 11. (Photo by Toshifumi Kitamura/AFP Photo)

Skulls are seen at the witch doctor kiosk during the day of offerings to the “Pachamama” (Mother Earth) in El Alto, Bolivia, August 1, 2016. Pachamama is a goddess revered by the indigenous people of the Andes. She is also known as the earth/time mother. In Inca mythology, Pachamama is a fertility goddess who presides over planting and harvesting, embodies the mountains, and causes earthquakes. (Photo by David Mercado/Reuters)