Ask a seller what they sold last month and they’ll answer instantly. Ask what that stock actually cost them, and the answer is usually a shrug or a rough guess.
It sounds like a small detail. It isn’t. Product cost is one of the biggest factors in most profit calculations — and if it’s wrong, every margin you look at is wrong too.
Why “what I paid” is harder than it looks
If you only ever bought a product once, at one price, this would be easy. Real buying isn’t like that. You restock the same product again and again, and the price moves:
- January — 100 units at $5.00 each
- March — 100 units at $7.00 each
- May — 100 units at $9.00 each
Now you sell one. What did that unit cost — $5.00, $7.00 or $9.00? Most sellers quietly default to “whatever I paid last time”, which can be the highest or lowest price on the shelf. Multiply that error across hundreds of sales and your reported profit drifts a long way from reality.
Every purchase, at its actual cost
Inselan doesn’t flatten your buying history into one number. It keeps each purchase as a separate batch, preserving:
- the actual unit cost you paid,
- the quantity received (and how much is still left),
- the supplier and the purchase date,
- a link back to the incoming order it came from.
Inbound shipping on that purchase is spread across the batch too, so the cost reflects what it genuinely cost to get the stock onto your shelf — not just the sticker price on the invoice.
The result is a proper, auditable purchase history — instead of a single figure you typed in once and forgot.
A live weighted-average cost
Inselan keeps a weighted-average unit cost for each product, based on the stock currently remaining.
Using the example above:
- 100 units at $5.00
- 100 units at $7.00
- 100 units at $9.00
With all 300 units in stock, the weighted-average cost is $7.00 per unit.
When you sell stock, Inselan uses FIFO to decide which batch’s quantity is reduced first — but FIFO does not become the cost of that particular sale. The weighted-average cost is recalculated as inventory changes, and the current weighted-average cost is captured as the cost of goods sold (COGS) when the sale is recorded.
A quick example: say you have 100 units at $5.00 and 100 at $7.00 — a $6.00 weighted-average cost. You sell 20 units: the oldest batch is reduced first, but the sale is costed at the $6.00 weighted-average captured at the time of sale. The remaining stock is then recalculated from what’s left.
In short: FIFO is used for stock depletion, while weighted-average cost is used for inventory valuation and COGS.
Where this shows up
Because the cost is grounded in real batches, it flows straight into the numbers you actually make decisions on:
- Stock value — what your inventory is really worth right now, updated on every receipt and sale.
- Per-order profit — each order is costed using the product’s current weighted-average cost, alongside fees, shipping and packaging.
- Listing profitability — so you can see which products genuinely earn their place.
One consistent cost number, running quietly under everything.
A few honest notes
- This tracks what you paid. For opening stock or a manual stock adjustment, Inselan uses the cost you enter (or your best-known cost) until better data comes in — so it’s worth filling those in.
- Inbound shipping is folded into batch cost automatically; one-off extras like import duty or tax aren’t added for you, so include them where they matter to you.
- Record your purchase costs in your accounting currency so the weighted average remains consistent.
Stop guessing your biggest cost
Revenue is easy to see. Real cost is where profit quietly leaks — and “roughly what I paid” isn’t good enough once you’re shipping at volume.
In Inselan, inventory costing is built in: every purchase kept as a real batch, a live weighted-average cost per product, and that same honest number flowing through your stock value, order profit and listing profitability — so you always know what your stock actually cost.