>>3309806Each lens has its own research and development costs that need to be recouped from lens sales. If it took more man-hours to design the 20mm lens than the 30mm lens, then the cost of paying the R&D team for their work, AS WELL AS the opportunity cost of NOT using the R&D team for other things, needs to be factored into the price.
The cost of construction is a factor. Some lenses are easier to build by virtue of having fewer elements, while others have lower standards and fewer QC steps that make them faster to build. Some lenses are made in factories that cost less to operate. A factory in Japan doesn't only cost more because of labor costs. The cost of the real estate, taxes, insurance, utililities, maintenance (and different building codes that might not require certain types of costly maintenance in third world countries) all go into the price of the products that come out of the factory.
With less popular lenses, supply and demand is likely also a factor. On /k/, you'll hear people complain that .32 ACP ammunition costs about twice as much as 9mm ammunition, even though a .32 cartridge has about 50% less of the same basic raw materials (brass, lead, copper, gunpowder, etc.) than the 9mm cartridge. That's because both cartridges are made on the same machines in the factory. The time spent to manufacture a box of .32 ammo that will sit on store shelves for longer and sell fewer units, regardless of the price, is time not spent manufacturing 9mm, which consumers buy the shit out of. With lenses, people love certain focal lengths, but don't really care for, or don't know how to use, others. I have noticed that 35mm are widely considered a useful lens for environmental portraits, but the same photographers complain that 24mm is "too wide," which just means they don't know how to use that focal length lens. People have it in their heads that there are legitimate reasons why certain focal lengths are popular, so certain focal lengths just don't sell.
