A supplier writes to say prices are going up 6%. It is tempting to put 6% into the forecast and move on. But a 6% price increase is not the same thing as a 6% cost increase — and treating them as the same can hide both problems and opportunities.
Price inflation describes what happens to the unit price you pay. Cost inflation describes what happens to the total cost of making your products. The two are connected, but the cost of a product also depends on how much you use, how much you make, what you make and how it is specified.
Price is one driver. Cost is the result.
For most materials and bought-in components, the cost of making a product can be broken down like this:
Cost = Volume × Quantity per unit × Price
Price inflation moves only the last term. If the other two also move — and in a manufacturing business they almost always do — the change in total cost can be very different from the headline price increase.
Take a component that costs £4.00 and is used three times in each product. The supplier increases the price by 6% to £4.24.
| Scenario | Usage per product | Cost per product | Change |
|---|---|---|---|
| Before the increase | 3.0 | £12.00 | — |
| Price up, usage unchanged | 3.0 | £12.72 | +6.0% |
| Price up, usage improved | 2.8 | £11.87 | −1.1% |
| Price up, usage worse | 3.2 | £13.57 | +13.1% |
The supplier's increase is identical in all three cases. The cost outcome ranges from a small saving to an increase of more than double the headline rate. The price letter alone does not tell you what will happen to cost.
Build a price, quantity and volume bridge
The most useful way to separate the two is a simple cost bridge. Imagine a material line where:
- Last year: 50,000 products × 2.5 units each × £4.00 = £500,000
- This year: 54,000 products × 2.6 units each × £4.20 = £589,680
Spend is up £89,680, or almost 18%. The price increase was 5%. So where did the rest come from?
| Driver | Calculation | Impact |
|---|---|---|
| Volume | 4,000 more products × 2.5 × £4.00 | £40,000 |
| Quantity per product | 54,000 × 0.1 more units × £4.00 | £21,600 |
| Price | 54,000 × 2.6 × £0.20 increase | £28,080 |
| Total | £89,680 |
Less than a third of the increase is genuinely price. Nearly half is volume — which is not a cost problem at all if the extra products were sold at a margin. And £21,600 is consumption: the business is using more material per product than it used to, and nobody has asked why.
If the whole increase had been explained as "inflation", the consumption problem would have disappeared into the budget.
Your inflation is not the published inflation
A second trap is applying a single inflation rate — a published index, or a figure from a trade body — across the whole cost base. Every manufacturer buys a different basket, and the movement in that basket can be very different from the headline number.
| Category | Share of spend | Price movement | Weighted effect |
|---|---|---|---|
| Steel and raw materials | 40% | +2% | +0.80% |
| Packaging | 15% | +9% | +1.35% |
| Energy | 25% | −10% | −2.50% |
| Consumables | 20% | +5% | +1.00% |
| Your basket | 100% | +0.65% |
In this illustration, a business that budgeted a blanket 4% would be carrying more than three points of cost that its own basket does not justify — while packaging, the category actually rising fastest, gets no particular attention. The right rate is the one built from your own spend, category by category.
Other things that look like inflation but aren't
- Mix: producing more of a material-heavy product raises average cost per unit without any price moving.
- Specification: a design change, new component or upgraded material changes what you buy, not what it costs.
- Currency: an unchanged price in euros or dollars can still cost more in sterling.
- Buying behaviour: smaller, more frequent or urgent orders often carry higher unit prices and freight costs.
- Contract terms: index-linked clauses, surcharges and minimum order quantities can move cost independently of the list price.
Each of these has a different owner and a different fix. None of them is solved by negotiating the percentage on a price letter.
Questions to ask before accepting a price increase
1. What is the increase based on?
Ask which underlying costs have moved and by how much. A request linked to a specific input should be explainable with evidence.
2. Does it apply to everything?
Blanket increases across a whole price list are rarely justified evenly across every item.
3. Has the underlying input already fallen back?
Increases made when an input peaks are not always reversed when it eases. Contracts should work in both directions.
4. What is it worth to us?
Multiply the increase by your forecast volume and usage. A few pence per unit becomes a material number at scale — and tells you how much effort the negotiation deserves.
5. What else is moving on this line?
Check usage per product and volume at the same time. The price may not be the biggest problem.
The practical takeaway
Price inflation is an input. Cost inflation is an outcome. Budgets, forecasts and supplier negotiations are stronger when the two are kept apart, because each driver needs a different response: price is a commercial conversation, quantity is an operational one, volume and mix are a sales and planning question, and specification belongs to engineering.
When those drivers are bundled into a single "inflation" number, the business loses sight of the parts it can actually control.
For a worked example of how this affects budgeting, see why your manufacturing budget may be wrong.
Is your manufacturing cost base telling you the whole story?
If cost is moving and the explanation doesn't quite add up, a short, confidential conversation is usually enough to see whether there is an opportunity worth investigating.
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