Calculator for app development cost estimation focusing on API Integration Specialists in the US, Australia, and the UK for Travel Aggregator applications. These apps pull data from numerous sources (airlines, hotels, car rental agencies, tour operators) to provide users with comprehensive search and booking options. Experienced API integration developers in the US, Sydney/Melbourne (AU), and London (UK) are crucial. The main cost drivers are the number and complexity of third-party APIs to be integrated (e.g., GDS systems like Amadeus, Sabre, Travelfusion; hotel APIs like Expedia, Booking.com; flight status APIs), managing different data formats (XML, JSON), handling API rate limits and authentication protocols, and ensuring real-time data synchronization. The calculator will factor in the development of a robust backend to aggregate and normalize data from various sources, implement complex search and filtering logic, and manage booking transactions. User interface design for presenting large amounts of information clearly and facilitating easy comparison is also important. Ongoing costs include API subscription fees, maintenance to handle changes in third-party APIs, and monitoring API performance and reliability.