Make-Buy Network

Make vs Buy Analysis: How Manufacturers Frame the Decision

Make vs. buy analysis compares fully loaded internal cost against external supply cost including freight, quality, and lead time. Here is how to build a correct comparison and avoid common mistakes.

Make vs. buy analysis starts with the relevant cost comparison, not the plant's full absorption cost by default. Internal make cost = direct material + direct labor + variable overhead + tooling amortization + quality cost, while fixed overhead is only relevant if the work will consume capacity that is already fully utilized. If the machine has spare capacity, most fixed plant cost does not change when you add one more part number. This is the mistake that causes many teams to outsource work that should stay inside, or keep work inside that is actually more expensive to run.

Buy cost has to include more than the supplier's quoted piece price. External supply cost = purchase price + freight + incoming inspection cost + supplier management cost + inventory carrying cost for lead time + expected quality risk cost. A supplier quoting $14.50 per part may look cheaper than a $12.00 internal cost, but adding $0.85 freight, $0.30 incoming inspection, $0.40 supplier management, $0.60 inventory carrying cost, and $0.35 quality risk premium brings the real outside cost to $17.00. Those extra inputs usually come from freight history, quality debit data, buyer workload, and inventory carrying rate used by finance.

Strategic factors matter when the cost comparison is close. A supplier may have better process capability, better surface finish, or a lower defect rate that justifies paying more for an externally made part. On the other hand, a single-source supplier for a critical component can create serious delivery risk that an internal process avoids. Capacity flexibility matters too, because internal production often responds faster to demand spikes than a supplier already running near full load.

Sensitivity analysis is what keeps a make vs. buy decision honest. Build a base case and then test what happens if volume drops 20%, freight rises 15%, scrap doubles, or supplier lead time stretches by two weeks. If the decision flips under a small change in assumptions, the answer is not robust and management should treat the choice as higher risk. Many bad sourcing decisions happen because teams present a single point estimate as if it were certain.

Use the result to set sourcing strategy, not just to approve or reject one quote. Review make vs. buy whenever demand changes materially, a machine is added or retired, a supplier reprices, or new process technology changes the internal cost structure. A comparison that was right three years ago can be wrong today because utilization, depreciation, and quality performance have moved. The best use of the analysis is an annual review that ties operations, procurement, and finance to the same numbers before margin starts leaking out of the network.

Published 2026-05-28.