FBA Fee Discrepancies
FBA fee discrepancies may occur due to the fact that Amazon’s monthly storage fees can vary from month to month.
If a user discovers that the FBA fees reported by MarketScout do not match the FBA fees reported by Amazon, the most likely reason is that the batch was run at the end of September or at the end of December.
You may use the FBA Revenue Calculator to see real-time cost comparisons between your fulfillment and Amazon's offering for customer orders fulfilled on Amazon.com.
For more information on Amazon's inventory storage fees, click here.