In Mumbai, the windows of new high-rise apartment blocks, old low-rise residential buildings and shantytown shacks portray the disparity in living conditions and incomes in the Indian city. Rents for a place to live range from more than $2,000 to less than $5 a month. Here: Windows and doors of an old residential building are pictured in central Mumbai October 10, 2014. The cost for buying a residential apartment in Mumbai close to the city centre ranges from 12,000 Indian rupees ($ 200) per square feet to 112,552 Indian rupees ($ 1800) per square feet. (Photo by Danish Siddiqui/Reuters)

Aegean airlines air hostesses take selfies after a news conference in Athens, Wednesday, March 28, 2018. In a deal worth up to $5 billion, Greek airline Aegean says it will buy 30 new Airbus aircraft, with the option of an additional 12, to upgrade its fleet as the country expects to break tourism records. The signing of the final purchase agreement is expected in June. (Photo by Petros Giannakouris/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.

In this August 24, 2018 photo, Changlair Aristide pauses for a portrait, wearing his protective clothing, including an old U.N. peacekeeper's jacket he found in the trash, before scavenging the Truitier landfill in the Cite Soleil slum of Port-au-Prince, Haiti. Before 2004, Aristide recalled having enough money to splurge on shoes, T-shirts and pants, but this year he could not buy his kids anything new for the school year. “Life is like that, up and down”, Aristide said. “They'll go to school anyway, even if I have to sell my pig. I love them”. (Photo by Dieu Nalio Chery/AP Photo)

A worker makes auto parts on a machine inside a workshop in Faridabad, India, December 24, 2015. Car makers such as Maruti Suzuki India and Hyundai Motor see huge growth in India, set to become the world's third-largest auto market by 2020 as millions buy their first new car. Price tags can be as low as $3,000 for a new Tata Motors Nano mini-car. India is also becoming a low-cost export hub for global car makers such as General Motors and Ford Motor. As the sector expands, some of the work is sub-contracted out to small factories operating on paper-thin margins, where poor contract workers often have little or no access to safety equipment or health benefits. (Photo by Adnan Abidi/Reuters)

Faruk, 17, a Rohingya refugee trader holds betel leaves which are on sale at a stall in Palong Khali refugee camp near Cox's Bazar, Bangladesh, November 3, 2017. He left his village in Myanmar when the military opened fire towards the Rohingya. “I buy this betel leaf from Palong Khali market, in one bundle there are 160 pieces, I buy it for 80 taka and I sell it for 100 taka (1 Bangladeshi Taka = 0.012 US Dollar). Bangladeshi's and I sell for the same rate in the camp. Outside in the local market it is 80 taka per bundle. My problem is that I don't have money so I can't buy anything to eat, I can't buy fish to eat”, he said. (Photo by Hannah McKay/Reuters)

Afghan children buy breads from a bakery in Fayzabad of Badakhshan province on February 7, 2024. (Photo by Omer Abrar/AFP Photo)

People carry an empty coffin past a street food vendor into the shop that is buying it to repair and sell in Port-au-Prince, Haiti, Friday, September 13, 2024. (Photo by Odelyn Joseph/AP Photo)