MiG-15 jet fighters are pictured in Kucova Air Base in Kucova, Albania on October 3, 2018. Albania retired its 224 Soviet- and Chinese-made MiGs in 2005, and since 2009 NATO neighbors Italy and Greece monitor its airspace. That led to economic decline in and around Kucova, which was called “Stalin City” during the era of Communist rule. (Photo by Florion Goga/Reuters)

Participant rides a carousel at the women's-only Petrolettes motorcycle festival on July 21, 2018 in Milmersdorf, near Berlin in Germany. Around 300 bike women from across Europe come together for the third edition of the festival. Women connect their passion for high speed motorbikes with music, movies, races, yoga etc. Festival that goes for three days was initiated by a group of female motorbike riders called The Curves. (Photo by Maja Hitij/Getty Images)

Pokot men carry a part of a carcass of a bull killed by a young man during an initiation ceremony in Baringo County, Kenya, January 20, 2016. Far from the bustling city of Nairobi, in an isolated corner of Kenya's Rift Valley, young men from the Pokot community spear a bull in a ceremony called Sapana that takes them into adulthood. (Photo by Siegfried Modola/Reuters)

A staff member removes a coffin from a room of the “Corpse Hotel” in Kawasaki, Japan, April 20, 2016. Many so-called corpse hotels have emerged as a flourishing business in the city following a crunch in crematoriums. Families can rent a room in Sousou on a daily charge of 9,000 Japanese yen (£58, €74, $84) to keep the body of the deceased relative for up to four days until they find a crematorium. (Photo by Thomas Peter/Reuters)

Somalis remove the body of a man killed in a blast in the capital Mogadishu, Somalia Saturday, October 14, 2017. A huge explosion from a truck bomb has killed at least 20 people in Somalia's capital, police said Saturday, as shaken residents called it the most powerful blast they'd heard in years. (Photo by Farah Abdi Warsameh/AP Photo)

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.

Huellas, a paraplegic dog in a wheelchair, walks at Pescadores beach in Chorrillos, Lima, September 7, 2015. Sara Moran has an animal shelter called Milagros Perrunos where she cares for stray dogs and shelters dogs injured from traffic accidents or domestic abuses. With donations and raffle, Moran purchases wheelchairs, food and medical treatment for the dogs at her shelter. (Photo by Mariana Bazo/Reuters)

A man sleeps between tombstones in front of his single-room home on a hot night in the Cairo Necropolis, Egypt, October 13, 2015. In the sprawling Cairo Necropolis, known as the City of the Dead, life and death are side by side. Amid a housing crisis in Egypt, and with the population of greater Cairo estimated at about 20 million, people count themselves lucky to have a place to call home in the graveyards that date back hundreds of years. (Photo by Asmaa Waguih/Reuters)