A visitor tries out the new glass Skywalk at the top of the refurbished Blackpool Tower on September 1, 2011 in Blackpool, England. After a GBP Ј20 million refurbishment, the iconic seaside Blackpool Tower opened today to the general public. The observation deck at the top of the tower becomes the Blackpool Tower Eye and features a skywalk made of glass overlooking the sea and the promenade. The opening is part of Blackpool's GBP Ј250 million GBP regeneration project. (Photo by Christopher Furlong/Getty Images)

Kha Tu Ngoc rests in her two- square- meter house in Ho Chi Minh City on May 2, 2018. The “micro- house” dwellings are dotted throughout Vietnam' s bustling southern hub, occupied by families clinging to postage stamp- sized plots a city developing at breakneck pace. Tucked away in winding alleys, nestled under new condo developments or sandwiched between street food stalls and shops, the tiny houses are easily missed by the unattentive passerby. (Photo by Thanh Nguyen/AFP Photo)

An elephant calf yawns as mahouts paint elephants ahead of celebrations for the water festival of Songkran in Ayutthaya, Thailand on April 11, 2019. The annual elephant Songkran event is held to promote the tourism industry. Songkran Festival is held also to mark the Thai traditional New Year falling annually on 13 April, and it is celebrated with people splashing water and putting powder on each other faces as a symbolic sign of cleansing and washing away the sins from the past year. (Photo by Soe Zeya Tun/Reuters)

A woman is cooled down with a watering can as she sunbathes using insulating tape, at a beauty center in Belo Horizonte, Brazil, on December 21, 2017. Brazilian women take advantage of the beginning of the summer to sunbathe using the new national trend: natural tanning with insulating tape. Instead of using tiny bikinis on the beach, women avoid being bothered or stalked by getting taped in the shape of them, and lay in the sun over rooftops to enjoy the morning sun and get the perfect “marquinha” tan lines. (Photo by Douglas Magno/AFP 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.

A bride gets her make-up done before the start of a mass marriage ceremony in Kolkata, India, February 14, 2016. A total of 150 tribal Hindu, Muslim and Christian couples from various villages across the state took their wedding vows on Sunday during the day-long mass marriage ceremony organised by a social organisation, the organisers said. (Photo by Rupak De Chowdhuri/Reuters)

A masquerader from the Paramin Blue Devils parades before judges during the traditional mas competition held by the National Carnival Commission at Victoria Square, in the capital Port-of-Spain, February 12, 2015. (Photo by Andrea De Silva/Reuters)

The Mil Mi-28 N military helicopter is seen at the MAKS 2019 air show in Zhukovsky, outside Moscow, Russia, August 27, 2019. (Photo by Maxim Shemetov/Reuters)