Originally posted by biz-engineer unless the lens design and manufacturing are outsourced (could be a valid model as well).
I think its really complicated. There are computer programs that help with lens designs (there was discussion on how computer aid is changing lens designs), there are various companies that produce special parts (aspheric or elements with special materials), different lens coating methods, factories that make specific parts (like mount, aperture blades, distance scales, AF motors), factories that put together the lens barrel.. parts of these can be outsourced, or even the whole chain. And its not the same for all lenses. We know some were done in cooperation with other companies, we know Pentax bought some Tamron designs, and we know third parties bought some Pentax designs (Tamron, Tokina, I think). It would be interesting to know, but I don't think we, the consumers, will ever get all these details.
Similarly to cars. A car is a certain brand, but that brand belongs to another conglomerate, and it has parts made by contractors and third parties, etc. etc. Modern day manufacture is really complicated and outsourcing is common. Traditional designs, which Pentax was famous for and was evolving for decades, are disappearing in favor of
bam! pow! designs that are made by the next computer program and excel in some new way (but have unknown weaknesses)