The quotation that is 18% lower usually left out three things

One: tooling and fixtures

The low quote often prices the mould but not the trial shots, or prices both and leaves out the revisions. Ask how many rounds of tooling change are included. Two factories can differ by a week of production and a five-figure sum on that line alone.

Two: inspection and packing

Full inspection, the inspection report, inner boxes, desiccant, pallet marking — these are separate lines in a honest quote and absent in a cheap one. They reappear later as a surcharge, at the point where you cannot move the goods without agreeing to it.

Three: rework and scrap

Every process has a yield. A quote that assumes zero rework is not optimistic, it is incomplete: the cost comes back as a delay or as a batch you pay for twice. Ask what yield the price assumes.

How to check it

Send the same bill of materials and the same inspection standard to every supplier, and ask each to mark every line as included, excluded, or extra. Compare the marked sheets, not the totals. The 18% usually turns into 4% or disappears.