FBA sellers must pay storage fees for products stored in amazon’s warehouses. The current prices for US-based warehouses vary by time of the year and product size (standard or oversize products):
January-September: $0.64 per cubic foot standard size and $0.43 for oversize products
October-December: $2.35 per cubic foot standard size and $1.15 for oversize products
Additionally, huge long-term storage fees are applied to items that are stored longer than 6 or 12 months as of the Inventory Cleanup date ($11.25 and $22.50 per cubic foot respectively).
As you can see, calculating exact storage fees for products stored on amazon is pretty hard (especially because of varying stock).
sellerboard uses the actual numbers which were charged by amazon rather than calculating them based on the volume of the products stored. They are automatically included into profit calculation, along with the number of other types of fees charged by amazon.
Get 1 month of free sellerboard usage by clicking on this link: https://goo.gl/S51czL