Google Photos offers unlimited free storage for photos and videos, which is a very attractive feature for users. However, it is important to note that this product is not actually free - users pay for it with their data. Google uses the photos and videos uploaded to Google Photos to improve its machine learning algorithms, which allows the company to better understand and target users with ads. As for the cost of storage, it is difficult to estimate without knowing the specific infrastructure and technology used by Google Photos. However, it is safe to assume that the cost of providing unlimited storage to millions of users is significant. Despite this cost, Google likely sees Google Photos as a way to attract and retain users within its ecosystem, which can lead to increased engagement and revenue in other areas of the business. Overall, Google Photos is a strategic product that serves multiple purposes for the company beyond simply providing a free and convenient storage solution for users.