That's a good question! Because we are an open platform, there is no cost to you to develop your application using any of the APIs in the sandbox. When you are ready to transition to production use of the APIs, there are fees for each of the APIs that are used. Fees are evaluated by application, as they are a function of many elements, including the nature of your application and your relationship with any existing Visa partner(s). We treat production applications on a case-by-case basis and work with you to determine appropriate pricing.