Two extrusion suppliers can quote the same 6063 profile at noticeably different prices per kilogram, and the gap is rarely the press. A per-kilogram figure is a compressed summary of six or seven separate cost decisions — alloy, conversion, die, finish, machining, packing and freight — and each one moves the number for a different reason. Buyers who compare only the headline $/kg are usually comparing which supplier amortised the die most aggressively, not which supplier will deliver the lowest landed cost per finished part.
This breakdown separates those layers, so you can see where your money actually goes and which levers you control.
Why the Per-Kilogram Quote Is Not the Price You Pay
Aluminium itself is a commodity priced daily on a metal exchange. The profile you receive is not. Between the billet and the box on your loading dock, the metal passes through a press, a die, a heat-treatment furnace, an anodizing line, possibly a machining cell, and a packing line. Every one of those steps adds cost, and several of them add cost in ways that scale with geometry rather than with weight.
That is the core problem with $/kg as a comparison metric: a heavy, simple profile and a light, complex one can carry the same headline rate while differing by a wide margin in cost per finished piece. When the part you actually buy is measured in pieces, the quote should eventually be converted into a piece price before you sign.
The Seven Cost Layers Inside a Per-Kilogram Quote
| Layer | What it covers | What drives it up |
|---|---|---|
| 1. Billet | Raw aluminium plus alloying elements | Alloy grade, billet premium, scrap and recovery rate |
| 2. Conversion | Press time, labour, energy, production yield | Press tonnage, section complexity, wall thickness, scrap rate |
| 3. Die | Tooling, trial, maintenance, replacement | Hollow vs solid, number of cavities, order quantity |
| 4. Finishing | Anodizing, powder coating, mechanical finish | Micron thickness, colour, masking, surface area |
| 5. Machining | Cutting, drilling, tapping, CNC | Tolerance, number of operations, fixturing |
| 6. Packing | Interleaving, wrapping, crating, labelling | Surface protection, export distance, pallet spec |
| 7. Freight & duty | Inland haulage, ocean freight, insurance, tariffs | Incoterm, volume, destination, duty rate |
Layer 1 — Billet: Alloy, Premium and Recovery
Billet cost tracks the metal exchange price plus a conversion premium that depends on alloy and diameter. 6063 is the workhorse for heat sinks and architectural profiles and normally carries a smaller premium than 6061 or 6005A, because it extrudes more easily and is produced in higher volume. Specifying 6061 “just to be safe” is one of the most common and most expensive habits in profile procurement: it raises the billet premium, narrows the extrusion window and usually forces a slower press speed.
Recovery matters as much as price. Every kilogram of billet that becomes scrap — butt ends, start-up scrap, reject lengths, machining chips — has to be paid for twice: once as purchased metal and once as the cost of converting it into something you cannot sell. A supplier who reports yield per order is telling you more about your real cost than a supplier who quotes a lower headline rate with an undisclosed scrap allowance.
Layer 2 — Conversion: Press Tonnage, Complexity and Yield
Conversion is the charge for turning billet into profile, and it is where two apparently identical quotes diverge most. The variables are the press the section runs on, the speed it can be run, the scrap generated at start-up and the labour and energy consumed per tonne.
- Press tonnage. A large press costs more per hour. If your section fits a smaller press, running it there is cheaper — but only if the die can take the pressure.
- Wall thickness. Thin walls are harder to fill and tolerate less variation. Very thin fins may need a slower ram speed, which spreads the same tonnage over fewer metres.
- Section complexity. Hollow sections with internal webs, multiple cavities and tight tolerances require more die support and more careful puller settings.
- Order length. Setup cost is fixed per run. A 300 kg order and a 3,000 kg order of the same profile do not carry the same conversion rate per kilogram.
Layer 3 — Die Amortisation: The Cost That Depends on Your Order Size
The die is a one-off tooling cost, but it is almost never quoted as a separate line the first time. It is folded into the per-kilogram rate and recovered over an assumed quantity. This is the single biggest reason two quotes for the same drawing can differ by a wide margin while both suppliers are being honest.
Ask two questions before comparing: is the die cost included, and over how many kilograms was it amortised? A supplier who amortises a die over 500 kg is charging you the full tool in the first order; a supplier who amortises it over 20 tonnes is assuming repeat business you may never place. Neither is wrong, but the headline rates are not comparable.
Also confirm die ownership and maintenance. If the tool is charged to you, it should be your property, and the agreement should state who pays for polishing, nitriding and replacement after the die reaches the end of its life.
Layer 4 — Finishing: Microns, Colour and Masking
Finishing is priced by surface area and process time, not by weight — which means a thin, finned heat sink can cost more to finish per kilogram than a heavy structural profile. Anodizing cost rises with target thickness, with the number of colour steps and with any area that must be masked before the bath. Powder coating adds pretreatment, curing and, for outdoor exposure, a qualification standard the supplier has to hold.
Specify the finish by standard and thickness rather than by appearance alone. “Anodized” is not a specification; “anodized to 15 µm, sealed, colour matched to sample” is. The second version costs more to quote but far less to argue about at incoming inspection.
Layer 5 — Machining and Fabrication
Once a profile leaves the press, every additional operation adds a setup and a handling step. Cutting to length is cheap per piece; drilling, tapping, milling and deburring are not, because each one needs fixturing, inspection and a chance to scrap the part after most of its value has already been added.
Design decisions that reduce machining cost are usually available: an extruded hole instead of a drilled one, a screw boss instead of a tapped insert, a profile that self-locates instead of one that needs a jig. These changes are cheapest to make at the drawing stage and most expensive to make after the die is cut.
Layer 6 — Packing and Layer 7 — Freight and Duty
Packing cost scales with the level of protection the surface needs. A mill-finish structural profile can travel interleaved and strapped; a brushed anodized profile with a visible face needs film, foam and often individual wrapping. For export, add crate specification, moisture protection and labelling requirements.
Freight and duty sit outside the supplier’s control but inside your landed cost. Aluminium profiles are bulky relative to their value, so volumetric weight often governs the freight charge. The Incoterm decides where the supplier’s responsibility ends, and the destination duty rate is a function of alloy, finish and end use — not of the per-kilogram price you negotiated.
How to Compare Two Quotes Fairly
- Convert both quotes to a price per finished piece, including cutting, finishing and packing.
- Confirm whether the die is included, and over what quantity it was amortised.
- Ask for the yield or scrap allowance assumed in the conversion rate.
- Check that both quotes specify the same alloy, temper, tolerance standard and finish thickness.
- Confirm the Incoterm and whether export packing is included.
- Ask what the price does when the metal exchange moves — is there a monthly adjustment clause, and how is it calculated?
An Illustrative Structure, Not a Price List
As a rough illustration only — actual figures depend on alloy, geometry, quantity and market conditions at the time of order — a mill-finish 6063 profile bought in modest quantity usually has billet as its largest single layer, conversion as the second, and die amortisation as the layer that varies most between suppliers. Add anodizing and the finishing layer can approach or exceed conversion. Add machining and the balance shifts again toward labour and equipment time.
The useful conclusion is not a percentage. It is that the layer you can influence most is almost always the one you specified least precisely: the drawing. Wall thickness, alloy grade, tolerance class and finish callout set the cost of every layer downstream.
What to Send for an Accurate Quote
A dimensioned drawing with alloy and temper, the tolerance standard you need, the finish specification with thickness, the annual and per-order quantity, and the destination port. With those five items we can quote die feasibility, conversion and landed cost in one pass instead of three rounds of clarification.
Send your drawing or target specification to our team — we reply with a quote and die feasibility assessment within 24 hours.