Calculator for app development cost estimation focusing on Subscription Management and Payment Gateway Integration Experts in Australia, Singapore, and France for Software as a Service (SaaS) applications. This is critical for any SaaS product that relies on recurring revenue. Specialists in Sydney/Melbourne (AU), Singapore, and Paris (FR) with experience in platforms like Stripe, Braintree, Chargebee, or Zuora are valuable. Key cost drivers include integrating with chosen payment gateways, setting up various subscription plans (monthly, annual, tiered features), handling free trials and freemium models, managing upgrades, downgrades, and cancellations, automating billing and invoicing, and dealing with failed payments and dunning management. The calculator will consider the complexity of implementing usage-based billing, coupon and discount code functionality, and ensuring PCI compliance for handling payment information. Securely storing customer payment details (or using tokenization) is paramount. Backend logic to manage subscription statuses and entitlements is essential. Ongoing costs involve payment gateway fees, maintaining compliance, and adapting to new payment methods or regulatory changes (like PSD2 in Europe).