Eventbrite, the largest marketplace for live experiences, reports significant growth through its API, which has facilitated the creation of over 1 million events and contributed 15% to its gross ticket sales. The document outlines the business value of APIs, highlighting their role in increasing revenue, enhancing product functionality, and fostering innovation across various platforms such as Salesforce, WordPress, and SurveyMonkey. Ultimately, the emphasis is on the importance of API-first development for scaling operations and customer experiences.