The honest answer is “it depends.” But there's a clear logic to injection moulding pricing once you understand the two big numbers: the one-off tooling cost and the ongoing cost per part.
The Two Costs That Matter
Injection moulding cost comes down to two things. First, the mould tool, a one-off investment to create the steel or aluminium tool your parts come from. Second, the cost per part, the price of each moulded component once the tool exists.
Tooling is the larger up-front cost, but the cost per part is usually low. This is why injection moulding becomes more economical the more parts you make: the tooling cost is spread across the whole production run.
What Drives the Tooling Cost?
Part size and complexity, the number of cavities (how many parts the tool makes per cycle), the tool material, and any special features like sliders or inserts all affect tooling cost. A simple, single-cavity tool for a small part costs far less than a complex multi-cavity production tool.
For lower volumes, a simpler or aluminium tool can dramatically reduce the up-front cost. We always advise on the most economical tooling approach for your quantity. See mould toolmaking.
What Drives the Cost Per Part?
Material choice, part weight, cycle time (how long each shot takes), and any secondary operations like assembly or finishing. Engineering and filled materials cost more than commodity plastics, and larger or thicker parts use more material and take longer to cool.
How to Get an Accurate Price
To quote accurately we need your part geometry (a drawing, STEP file or sample), the material or performance requirements, and your expected annual quantity. The more you share, the more accurate the quote. See what information you need to get a quote.
Sources & Further Reading
For independent background on the process, see the British Plastics Federation's guide to injection moulding and the overview on Wikipedia.