2.2 · The Cost of One Sale

An order can show $105 received and still add far less than $105 to the business. The difference is not one universal fee percentage. It is a set of costs that behave in different ways: some follow price, some occur once per order, some consume time, and some belong to a whole month. This chapter builds one management worksheet for one kind of order. It is a planning model, not a tax return or a complete set of accounts.

​

Give the worksheet a boundary

Costs change with venue, product, fulfillment method, account terms, and time. The final worksheet begins by recording its check date, sales venue and account type, product lane and typical order, and fulfillment method. For every live input, record where you found it. Use the venue’s current official schedule for its charges, an actual label quote for postage, your supply cost, your own task timing, and your records for losses and fixed expenses.

​

Keep costs in their natural form

Forcing every cost into a percentage makes the model look simple while hiding what changes it. A price-linked charge grows with the fee base. Postage may stay the same across several item prices. Labor follows time. A monthly subscription must be allocated across a stated period. The loss allowance gives returns, damage, fraud, or another occasional loss a visible place in the plan. This does not predict that a standard percentage will occur. If you have enough history, use it. If not, write the scenario you are choosing to model. Labor deserves its own line for the same reason. A sale that requires research, sorting, listing, storage, packing, and customer follow-up may look attractive when only cash outlays are counted. Measure the work first; decide what an hour should mean in your model second. If you have no completed-order history, use a clearly labeled planning scenario for the fixed- cost denominator and replace it after the first measured period. If you have no fixed operating cost for that period, enter zero. Do not present a planned order count as an observed one.

​

Build the cost function

Three short labels keep the worksheet compact:

• R is modeled order revenue: item price plus any shipping or handling amount retained by the business.
• C is the total modeled selling and fulfillment cost.
• Q is the inventory acquisition cost in your records.

The modeled selling and fulfillment cost is: **C = price-linked venue charge + per-order venue charge + postage + supplies + loss allowance

• labor + allocated fixed cost**

After the dollar model is complete, calculate a cost rate only when R > 0. If R = 0, the cost rate is not computable even though the dollar costs still are. Cost rate = C ÷ R Bring in Q only to see what this sale contributes after inventory and modeled selling costs: Modeled sale contribution = R − Q − C Contribution is a management result for this worksheet, not net profit, taxable income, or a complete accounting result.

​

Work one hypothetical order

Every number in this example is invented for teaching. The percentage is not a current venue rate, and the postage, labor value, loss allowance, and order count are not benchmarks.

• Item price = $100.00
• Shipping amount retained = $5.00
• Fee base = $105.00
• Price-linked rate = 10%
• Per-order charge = $0.30
• Postage = $4.50
• Supplies = $0.70
• Loss allowance = 2% of R = $2.10
• Labor = 0.25 hour × $20 = $5.00
• Fixed allocation = $30 of period cost ÷ 30 completed orders = $1.00

The model produces: R = $100.00 + $5.00 = $105.00 Price-linked venue charge = 10% × $105.00 = $10.50 C = $10.50 + $0.30 + $4.50 + $0.70 + $2.10 + $5.00 + $1.00 = $24.10 Cost rate = $24.10 ÷ $105.00 = 22.95% If Q was $60.00: Modeled sale contribution = $105.00 − $60.00 − $24.10 = $20.90 The example keeps shipping income and shipping costs separate. If you prefer to model only the shipping gap, define that method once and do not count the same shipping income or cost again.

​

Change one assumption

Fixed-cost allocation depends on the period and order count used. In the example, $30 spread over 30 completed orders adds $1 to each order. If the same $30 is spread over 10 orders, allocation becomes $3. With every other input unchanged: Revised cost = $26.10 Revised contribution = $18.90 Neither order count is presented as normal. The sensitivity check shows why a period cost cannot be copied into the model as if it always behaved like a fee on sale price.

​

Complete your dated worksheet

Replace every example input: Checked on: ___ Sales venue and account type: ___ Product lane and typical order: ___ Fulfillment method: ___ Modeled order revenue (R): $___ Source/date: ___ Verified price-linked and per-order venue charges: $___ Source/date: ___ Postage and supplies: $___ Quote/record date: ___ Explicit loss scenario or historical allowance: $___ Basis: ___ Labor: ___ hours from timing record/date ___ × $___ internal value based on ___ = $___ Fixed allocation: $___ period cost from record/date ___ ÷ ___ completed orders = $___ Total modeled selling and fulfillment cost (C): $___ Cost rate — C ÷ R: ___% Inventory cost (Q): $___ Inventory record/date: ___ Modeled sale contribution — R − Q − C: $___ Circle the two inputs most likely to change and write when you will check them again.