TL;DR Three practical options exist for tracking cheap Bali flights programmatically: SerpApi, Amadeus Self-Service, and direct scraping SerpApi is fastest to prototype; Amadeus gives authoritative GDS fare data with more setup friction Scraping is fragile and legally ambiguous; avoid it for anything beyond one-off checks Perth-Bali (A$300-420 return) and Sydney-Bali (from A$400) are the highes