Fixture: A fixture is a purpose-made device that holds and locates a specific part in the same position every time, for machining, welding, assembly or inspection.
Where a vice is general purpose, a fixture is built for one part or a family of parts, with locating pins, stops and clamps placed so that every part loads the same way. A jig is closely related: strictly, a jig also guides the tool, as a drill bushing does, though shops use the two words loosely.
What it means for the price
A fixture is a one-off cost, often treated as NRE or tooling: design time, material and machining. It pays back through faster loading, fewer errors and less setup on later batches. For a single prototype, a fixture rarely makes sense; for repeat production, it often does. A quote should show it as its own line, so a buyer who orders again does not pay for it twice.
Example: a €400 fixture that saves 3 minutes per part on a machine at €60 per hour saves €3 per part, so it pays back after about 133 parts. The figures are an example.
Common confusions
Fixture is one form of workholding, not a synonym for it. And a fixture in machining has nothing to do with a test fixture in software. Read how CNC setup time affects price.
Go deeper: Set-up time in CNC: the hidden cost in small batches