In-house fulfillment costs include warehouse rent, labor, equipment, insurance, utilities, software, and management time. Most brands only count rent and labor, missing 30–40% of actual cost.
A 3PL bundles those costs across many clients, which typically delivers unit economics that are hard to match in-house until you hit very high volume — usually 50,000+ units per month.
The hidden advantage of a 3PL is flexibility. You pay for what you use. In-house means paying for peak capacity year-round even when volume is low.
For brands doing 500–10,000 units per month, 3PL is almost always the right answer. The economics only flip at scale, and only if you have the management capacity to run a warehouse operation.