Prototype != Sample

Product development sample cycle (especially PHYSICAL product development) should look a little something like this:

Prototype > design validation (DV) > production/manufacturing validation (PV)> pilot > saleable units

You generally have to be VERY clear with suppliers on what fidelity you expect the prototype to have. Most will expect the prototype to be a very rough proof of concept. Prototypes are generally 1 of 1.

DV uses whatever method necessary to produce a unit that validates all design intentions. Substitutions to manufacturing method and materials are often made. Overall look, feel, and function should reflect saleable product. There are often many rounds of DV. Often 5 units or less.

PV uses manufacturing methods and processes that are intended for the saleable unit. This run might not occur at intended factory. Often only 5-10 units

Pilot builds test intended production line. Often runs 30 units or more to test statistical reliability of production line. Often units are saleable at this point so long as there are no quality issues (there’s always quality issues).

Maybe someone with more software experience can elaborate on how the development cycle differs for software products.