An estimate for 1,000 saleable units
Consider this illustrative shipment: $20,000 for goods, $2,000 for freight, $100 for insurance, an assumed $1,000 duty, $400 for handling and delivery, and $100 in payment costs.
The total is $23,600, or $23.60 per unit at 1,000 saleable units. All of these inputs are invented for planning. They are not current rates or a customs determination.
Check what each quote includes
Start with the goods price in the invoice currency and show the planning rate used to convert it. Add the freight, insurance, estimated duties, brokerage, handling and inland delivery that the buyer is expected to bear. Mark each amount as quoted, actual or assumed.
Read the scope of an all-in supplier or forwarder quote before adding separate charges. If it already includes delivery, adding the delivery cost again will inflate the result. Payment and FX costs also belong in the model only to the extent that they are not already included elsewhere.
Update the model when a quote changes and again when you receive the actual invoice. Keep the original budget beside the final cost and explain the differences. That record is useful when pricing and funding the next purchase, especially if a previously assumed charge turned out to be materially different.
Calculate customs value separately
Applying a duty percentage to the whole landed-cost subtotal can give the wrong answer. CBP explains that separately identifiable international freight and insurance are generally excluded from US transaction value. Required additions can include certain assists, packing, royalties and other amounts; the appropriate valuation depends on the transaction.
Use a separate customs-value input agreed with your broker. Show ordinary duty, any additional measures, fees and other charges separately. A calculator with one assumed percentage cannot determine the legal classification or every charge that applies.