There are a lot of ways companies can rack up high bills for using cloud services, sometimes unexpectedly. One particularly stiff expense is the cost of shifting data from one cloud provider’s servers to another provider, or to a company’s own data center. The Information has learned just how much some companies have had to pay for these “data transfer” costs, as they’re called.

The chart above shows how much 10 of the top customers of Amazon Web Services—the dominant cloud provider—paid for data transfer services in 2017 and 2018. The chart, which is based on internal AWS sales figures obtained by The Information, show that data transfer charges for one customer, Apple, approached $50 million in 2017. That represented about 6.5% of Apple’s total AWS bill of $775 million for that year, the sales figures show.

Seven of the 10 companies saw increases of at least 50% in their AWS data transfer bills last year compared to the year before.