What Drives CNC Prototype Cost, Line by Line
A prototype quote for a single machined bracket often lands between $450 and $900, and buyers reasonably ask why a part with $10 of aluminum in it costs seventy times the material. The answer is not margin. It is that a prototype is mostly engineering labour wearing a part-shaped hat, and only a small fraction of the hours in that quote touch metal. Understanding the split tells you which cost lines are negotiable, which are physics, and why asking for three parts instead of one does not triple the invoice.
The four buckets in every prototype quote
Almost every quote you receive decomposes into four groups. Non-recurring engineering covers CAM programming, toolpath verification and any custom fixture design. Setup covers loading tools, finding zero, proving the first cut and adjusting offsets. Variable cost covers material, run time, finishing and packaging. Verification covers inspection and documentation.
On a one-off part, NRE and setup typically account for 55 to 70 percent of the price. At 50 pieces the same two buckets fall to 15 to 25 percent. Nothing about the part changed; only the denominator moved.
Programming and setup do not scale
Programming a three-axis part with 20 features takes 3 to 5 hours for a competent programmer working from a clean model: importing, orienting, choosing tool sequences, generating paths, simulating for gouges and collisions, and writing the setup sheet. At $45 to $60 per hour, that is $135 to $300 before a cutter touches stock.
Setup on the machine is 1.5 to 2.5 hours for a first article: mounting the vise or fixture, indicating it, loading the tool carousel, touching off 8 to 14 tools, running the first part, measuring it, and adjusting. At $55 to $75 per hour of machine time, call it $90 to $180. Once the program is proven, a repeat setup for the same part drops to 20 to 40 minutes.
None of this repeats when you order the second and third piece. That is the entire reason the unit price curve falls so steeply at the start.
See also: The Real Cost of Holding Machined Parts in Inventory and Material Cost in Machining: The Share Most Buyers Underestimate.
Material minimums create a floor under the price
You cannot buy 0.9 kg of 6061. You buy a bar, and the saw operator charges for the cut. For a bracket that starts as 130 x 90 x 30 mm stock, the part weighs about 0.55 kg after machining but consumes roughly 0.9 kg of bar. At $8 to $11 per kilogram for 6061 plate or bar in Shenzhen, material is $7 to $10 per part — trivial.
What is not trivial is the minimum. Many shops will not open a purchase order for a single bar, so the quote carries a $40 to $80 material handling minimum, or prices the whole 3-metre bar and keeps the remainder. On a one-off, that minimum can be 8 to 12 percent of the total invoice even though the metal in your part is worth $9.
Finishing lot charges and inspection
Anodizing is priced per lot, not per part. A clear Type II anodize on small aluminum parts typically carries a $60 to $90 minimum lot charge plus $1 to $4 per part for handling and racking. One part costs $65; three parts cost $89; 100 parts cost $350. The first part is almost all lot charge, which is why a finish adds 10 to 14 percent to a single-unit prototype and 3 percent to a batch.
Inspection follows the same shape. A first article inspection on a bracketed part with 25 dimensions takes 1 to 1.5 hours on a CMM plus report writing: $60 to $110. Spot-checking parts two and three adds $10 each. If your drawing calls for a full dimensional report per piece, you have just converted a fixed cost into a variable one, and the curve flattens.
Why three identical parts cost about 1.6 times one
With one part, you pay the full NRE, the full setup, the whole fixture and the entire lot charge, and you get one part's worth of run time. With three parts, the NRE, the fixture and most of the setup stay exactly where they were. Only material, run time, deburr, per-part finishing and a light inspection repeat.
In the example below, the single part costs $729 and three cost $1,155 — a ratio of 1.58, not 3.00. The fourth part would add roughly $175. By the tenth, each additional piece adds about $160 and the average has fallen to around $290.
| Cost line | 1 piece | 3 pieces | Behaviour |
|---|---|---|---|
| CAM programming, 4.5 h | $210 | $210 | Fixed one-time |
| Machine setup, 2.0 h | $110 | $110 | Fixed per order |
| Soft jaws and fixture | $90 | $90 | Fixed one-time |
| Material, cut to length | $56 | $168 | Variable, $56 each |
| Machining, 70 min at $86/h | $100 | $300 | Variable |
| Deburr and hand finish | $26 | $78 | Variable |
| Clear anodize Type II | $65 | $109 | Lot charge plus per piece |
| FAI report and packing | $72 | $90 | Mostly fixed |
| Total | $729 | $1,155 | Index 1.00 / 1.58 |
Read the table as a negotiation map. The $410 of programming, setup and fixture is where a shop has discretion, and where a well-organized model, a complete drawing and a standard tolerance scheme genuinely reduce hours. The $168 of material and $300 of run time are physics — the only lever there is design, not supplier choice.
If you want the fixed block cut, the highest-leverage move is to relax tolerances that cost time without adding function. A ±0.01 mm tolerance on a pocket floor that sits against nothing forces a finishing pass, a tool change and a CMM check. Changing it to ±0.1 mm can remove 15 minutes of run time and 20 minutes of inspection on every part in the order.
Where the fixed block can legitimately shrink
Send a STEP file rather than a drawing plus a model that disagree. A model with unresolved geometry forces the programmer to rebuild surfaces, and rebuild time is billed at the same rate as programming.
Use standard stock sizes. A part designed around a 100 x 100 mm plate will be quoted from 100 x 100 stock; a part that needs 103 x 98 mm will be quoted from 110 x 110 and you will pay for the difference in both material and roughing time.
Ask whether the shop will quote the first article and the batch together. Many will hold the program and fixture and quote the follow-on 25 pieces at a materially lower unit price if they know it is coming. Our quoting process explains how we handle that handoff, and the contact page is where to send a model for a 24-hour quote with DFM notes.
Frequently asked questions
Why is one machined prototype so expensive compared with the material cost?
Because 60 percent or more of the price is programming, setup, fixture and inspection labour that exists regardless of part size. In a typical single-unit quote, $6 to $10 of aluminum sits alongside $410 of one-time engineering and machine preparation.
Does ordering three prototypes cost three times as much?
No. Expect about 1.6 times the single-unit price for three identical parts, because only material, run time and per-piece finishing repeat. The programming, fixture and most of the setup are absorbed by the first part.
Can I avoid the anodizing minimum charge on one part?
Only by changing the finish or the quantity. Lot charges of $60 to $90 are standard for small anodize loads. Alternatives include a chem film, which is often cheaper at low volume, or shipping the part bare and finishing it locally.
What is the fastest way to reduce a prototype quote?
Send a clean STEP file with tolerances that match function, specify standard stock sizes, and use one finish. Those three changes routinely remove 20 to 30 percent from a first-article quote without changing the part's performance.
Related reading
Send a drawing for a quote and DFM review.
STEP, IGES, X_T, PDF or DWG up to 50 MB. Tell us quantity and finish, and the quote comes back with tolerance and process notes, not just a price.