Exotic poolside scene that is supposed to make you believe that you are in New York or Sydney is shot right here in Mumbai with the help of tourist foreigner extras. For a day's work, they can earn Rs. 1000 - 5000, a meal, and a drop back to the hotel if the shooting goes into wee hours of the morning.
This type of casting does violate the norms related to recruitment and wages for junior artists. The model headhunters work with the hotel staff where the tourists are know to stay. They reach out discretely. They also bribe the local police to ensure that they are not pulled over for using the foreigners illegally in Hindi films.
There is something for everyone. The filmmakers use the foreigners as a marketing ploy to sell the film to the distributors for a higher price. The producers put up the sets inside studios and use foreigners to show that these sequences are filmed abroad. A Rs 10-lakh song sequence is presented as a Rs 50-lakh one.
Here is a list of Mumbai film studios. Maybe a stint in a Bollywood movie will pay for the higher air fares.