Custom assembly costs range wildly—from a few hundred dollars for simple hand-assembled prototypes to six figures for high-volume precision work. Understanding what actually drives those prices means knowing the difference between quoting a one-off job versus tooling for 10,000 units, and that's where most buyers get blindsided.
What Actually Gets Priced in Custom Assembly
Contract assemblers don't just charge for labor and parts. They're quoting material handling, setup time, quality control, overhead allocation, and equipment depreciation. A small order of 50 units will have a dramatically higher per-unit cost than 5,000 units because fixed setup costs get spread across fewer pieces.
The bill of materials (BOM) is usually the largest line item—parts themselves cost what they cost. But assemblers add margin on top, typically 15–30% depending on component sourcing complexity. If you're supplying components yourself, you'll see lower final quotes but still pay for receiving inspection, kitting, and storage.
Labor and Complexity Drive Real Variation
Hand assembly work averages $15–$45 per hour depending on location and skill level, but that's just the base rate. Technicians installing connectors, soldering delicate boards, or performing intricate mechanical assembly need training and cost more. A single board with 200 hand-placed components might take 45 minutes; the same work via pick-and-place automation takes 3 minutes and costs far less per unit at volume.
Complex assemblies—those involving mechanical fastening, potting, testing, or calibration—add stages that each have their own labor and material costs. A medical device assembly with IP67 sealing, functional testing, and traceability labeling will cost 2–3× more than basic electronics assembly.
Setup and tooling are the hidden killers on small runs. Changeover time to switch from your job to another customer's job might cost $500–$2,000 depending on complexity. At 100 units, that's $5–$20 per unit just for setup overhead.
Typical Price Ranges by Volume and Type
Simple electronics (PCB assembly, no mechanical components):
- 10–50 units: $8–$20 per unit
- 100–500 units: $4–$10 per unit
- 1,000+ units: $2–$5 per unit
Mechanical assembly (fastening, subassembly integration):
- 10–50 units: $15–$50 per unit
- 100–500 units: $8–$25 per unit
- 1,000+ units: $4–$15 per unit
Mixed electro-mechanical or precision work:
- 10–50 units: $25–$100+ per unit
- 100–500 units: $12–$50 per unit
- 1,000+ units: $6–$25 per unit
These are assembly labor only—add your BOM cost on top. Testing, packaging, and shipping typically add another 10–20% to the final invoice.
What Changes the Quote Most
- Volume commitment: Promise 10,000 units annually and prices drop 30–50% versus one-off prototype orders
- Documentation quality: A vague BOM gets quotes that include risk premiums; clear specs with drawings and standards reduce price
- Component sourcing: Asking an assembler to source hard-to-find parts adds 20–40% markup; supplying standard parts yourself saves money
- Quality and traceability: ISO-certified assembly with full lot traceability costs 15–25% more than basic work
- Lead times: Rush orders (1–2 week turnaround) are typically 20–50% more expensive than standard 4–6 week schedules
- Location: Domestic US assembly runs 30–60% more expensive than offshore, but includes shorter lead times and easier communication
How to Get Accurate Quotes
Prepare a complete BOM with part numbers and quantities. Include a reference design or technical drawing so assemblers understand mechanical fit, electrical connections, and any special handling needs. Specify your target volume (even if it's just a range) and desired delivery timeline—this fundamentally changes what assemblers will quote.
Request quotes from at least three providers. One will be the cheapest; one will be the highest. The middle option usually represents fair market value. Ask each for a line-item breakdown so you understand where money goes.
Testing and inspection standards matter enormously. Specify whether you need basic functional testing, AOI (automated optical inspection) on PCBs, or full burn-in. Each step adds cost but catches defects before products ship.
Services like Mercoly help you compare and connect with vetted Contract Assembly & Manufacturing providers side-by-side, making it easier to benchmark real quotes against industry standards.
Frequently Asked Questions
Q: Is offshore assembly always cheaper? Yes, labor costs are substantially lower overseas (50–70% savings on assembly labor), but international shipping, longer lead times, quality communication challenges, and potential tariffs can offset those gains on small orders.
Q: What if my BOM includes components I can't source? Tell your assembler up front; many have relationships with suppliers or can locate items. Expect a sourcing fee (typically 5–15% markup) and longer lead time, but it's usually faster than you hunting yourself.
Q: When is it worth paying for custom tooling or fixtures? Once you commit to 500+ units or an ongoing monthly volume, custom jigs pay for themselves by speeding assembly and reducing errors—typically recovering tooling costs within the first production run.
Get your first assembly quote comparison in minutes—connect with providers matched to your specific project on Mercoly.