Three are enough. Amazon's own FBA revenue calculator for marketplace fees, a real quote from a freight forwarder for landed cost, and a spreadsheet for the cash timeline. Budget $8,000 to $15,000 for a single product and $25,000 to $50,000 for a five-product brand.
The short version
- The fee side is solved. Amazon publishes a calculator that returns referral and fulfillment fees per unit once you know dimensions and weight.
- The landed cost side is not. No calculator knows your freight lane, duty rate or inspection cost. Quotes do.
- The spreadsheet does the work the calculators cannot. It models timing, and timing is what runs sellers out of cash.
- Size the market before you cost anything. We use a $2 million a year floor, because under that there is not enough revenue to capture profitably after acquisition cost.
- Validate before you scale. Phase one is 200 units and $5,000 to $10,000, with up to four products tested at once.
The sequence, with a gate at each step
Run these in order. Each step has a gate, and failing a gate is a cheap outcome compared with discovering the same thing after a container arrives.
Size the market. Estimate annual category revenue for the specific niche, not the department. Gate: below about $2 million a year, stop here. There is not enough revenue in the niche to capture profitably once you pay for customers. Tools: category ranking pages, Amazon's own opportunity reporting, and your own arithmetic of units times price.
Price the unit at the factory. Get three supplier quotes with minimum order quantity, tooling cost and unit cost at your target volume. Gate: a quote you can actually meet in cash. Tools: supplier platforms and direct factory contact, plus a written specification so all three quote the same product.
Price the freight and duty. A forwarder quote for your lane, your incoterms and your carton dimensions, plus the duty rate for your classification. Gate: landed cost per unit written down and dated. Tools: two forwarder quotes and your customs classification. Nothing else gets you this number honestly.
Price the marketplace. Run the landed cost and your intended retail price through Amazon's FBA revenue calculator. Gate: contribution margin per unit after referral and fulfillment fees. Tools: the calculator, your Seller Central fee preview once you are live, and the category return rate you researched in step one.
Price the validation run. Phase one is a deliberately small commitment: around 200 units and $5,000 to $10,000, and you can test as many as four products in parallel at that size. Gate: enough inventory to reach a real conversion signal without a warehouse full of a mistake.
Price the traffic. There is no hard minimum ad spend, but plan on about $1,000 a month if you want the data to be meaningful enough to optimize. Gate: a monthly figure you can fund for the whole test window, not one strong month.
Model the cash timeline. This is the spreadsheet. Deposit to factory, balance on shipment, freight in transit, receiving, first sale, first payout. Gate: your lowest cash point stays above zero with the reorder included.
The cost stack, in the order the money leaves
| Line | What it covers | Where the number comes from |
|---|---|---|
| Tooling and samples | Molds, samples, revisions | Supplier quote |
| Inventory | Unit cost times order quantity | Supplier quote at your quantity |
| Freight, duty, inspection | Door to warehouse | Forwarder quote plus duty rate |
| Amazon fees | Referral and fulfillment per unit | FBA revenue calculator |
| Brand setup | Trademark filing, photography, packaging design | Actual invoices, not estimates |
| Advertising | Launch spend | Your own plan, about $1,000 a month as a working floor |
| Management | Agency or your own time | Published fees, ours start at $800 a month for one product |
| Buffer | Returns, damage, a reorder that lands early | A line you fund before you need it |
Two of these lines are where beginners under-budget. The first is the buffer, because it feels like pessimism until the week you need it. The second is the second purchase order, which is usually due before the first one has paid you back.
Why the spreadsheet beats the calculator
A calculator answers "is this unit profitable". A spreadsheet answers "am I solvent in month four", and the second question is the one that ends businesses. Build twelve monthly columns. Put every outflow on the date it actually leaves, put marketplace payouts on the date they actually arrive, and read the lowest point of the row. That number is your real capital requirement, and it is almost always larger than the sum people write on a napkin.
Our sourcing frameworks were built across more than 500 brands, and the pattern is consistent: the products that fail on cash rarely fail on unit economics. They fail on timing.
What most agencies will not tell you
Most quotes arrive before anyone has sized your market. That order is backwards, and it is deliberate, because the sizing work is what might tell you not to buy anything at all. A number produced before the market analysis is a number produced without knowing whether the market can pay it.
The second thing: the fee is the smallest line in the stack. Inventory, freight and advertising dwarf it. If you are comparing agencies on monthly fee alone, you are optimizing the line that matters least while ignoring who is deciding how your inventory and ad budget get spent. Ask for a written cost model with your numbers in it before you sign anything, from us or anyone else.
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We will size your market and write the cost model before quoting anything, at no charge, at Flapen.
