The cost to build and operate a custodial wallet depends on security layers, tech stack, and user volume. For around 10,000 users, development and infrastructure might range between $40,000–$80,000, covering secure storage, KYC, and APIs. Scaling to 1,000,000 users can push costs above $250,000, mainly due to load balancing, database optimization, and compliance tools. Ongoing maintenance adds 15–25% annually for server management and updates. Overall, involves significant upfront and scaling expenses to ensure performance and regulatory reliability.