πΈ Full version with screenshots: https://tomi431.github.io/Tomi/2026/08/03/amazon-fba-fee-optimization
Amazon's FBA fee schedule has over 70 line items across size tiers, weight categories, and special handling classifications. Most sellers check the fulfillment fee on their product and move on. The ones optimizing margins check all of them.
Here are the three FBA costs most sellers overpay β and how to fix each one with data.
Fee Leak 1: Dimensional Tier Misclassification
Amazon periodically re-measures products in its fulfillment centers. If the automated measurement system captures a dimension slightly larger than your actual product β due to packaging bulge, an angled scan, or operator variance β your product gets bumped into a higher size tier. The fee difference can be $2-5 per unit, applied retroactively.
The fix: Download your Monthly Storage Fee report and Monthly FBA Fee report. For every ASIN, compare the current dimensional tier to the tier you expect based on your actual measurements. If you find discrepancies, dispute them with photographic evidence β a photo of the product next to a measuring tape, showing actual dimensions. File the dispute through Seller Central β FBA Issue β Remeasure Product.
# Pull product detail to cross-check FBA fee tier:
# product_detail β check dimensions against FBA rate card
A seller with 500 monthly units in a misclassified tier is losing $1,000-2,500 per month β $12,000-30,000 per year β to a measurement error they never checked.
Fee Leak 2: Storage Fees on Stale Inventory
Amazon charges monthly storage fees per cubic foot. After 181 days, an aged inventory surcharge (long-term storage fee) kicks in at $6.90+ per cubic foot. One unit of slow-moving inventory stored for 8 months can accumulate $3-5 in storage fees β on a product that already failed to sell.
The fix: Pull your Inventory Age report monthly. Flag any ASIN with inventory over 120 days old. For each flagged ASIN, calculate: storage fees paid to date Γ· units remaining. If this number exceeds 20% of the product's selling price, the product is costing more to store than it is worth. Create a removal order β liquidate, donate, or destroy.
Do this once a month. It takes 10 minutes. The alternative is paying storage fees on products you have already given up on.
Fee Leak 3: Unnecessary Prep Services
Amazon offers FBA Prep Services β labeling, poly bagging, bubble wrapping. These services cost $0.40-1.50 per unit. If your supplier or freight forwarder can do the same prep before shipping to Amazon, you save that fee on every unit. For a seller moving 2,000 units per month, that is $800-3,000 per month in avoidable costs.
The fix: Compare Amazon prep fees vs. supplier-side prep costs. If supplier prep is cheaper, update your shipping workflow: supplier preps β forwarder ships β Amazon receives without prep services. Update the FBA shipment settings to indicate "No Prep Required" for each applicable ASIN.
Try it yourself: git clone https://github.com/DannylydST/sorftime-seller-agent β python3 scripts/install.py β get your key at open-intl.sorftime.com
Originally published with screenshots at https://tomi431.github.io/Tomi/2026/08/03/amazon-fba-fee-optimization.
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