Dropbox makes money by selling paid subscriptions for a premium account. They offer a free account with a set storage size of two gigabytes, which incentivizes a user to join. Once a user runs out of storage space they are then incentivized to upgrade to a Standard, Advances, or Enterprise account for more storage space.

The next tier up from a Basic (free) account is the Standard account, which provides 5TB of storage space for $21/month.