Long-term storage is used only by transfers that are available for longer than 30 days (including also files stored forever - the ones without an expire date). Transfers that have an expiration shorter than 30 days do not occupy long-term storage.
Each Business user gets 100GB of long-term storage for free - that is included in the subscription price. When a user stores long-term data above that limit we apply a flat rate of $0.10 per GB per month. Storage fee is billed monthly.
Example: user stored 140GB (i.e. 40GB above the free-tier limit) of long-term data for 15 days in a 30-day month. The monthly bill is:
40GB x $0.10 x 15 days / 30 days = $2.00