Future of lens technology
Do the lenses prices reflect how complex to manufacture them?
or it is based on profitability and supply-demand analysis?
For example, 18-55 F/3.5-5.6 lenses are good yet cheap.
But 16-85 (same aperture) is far more expensive.
35 F/1.8 is cheap but 28 F/1.8 is way more expensive and so on.
Lens prices are based on how hard it is to make the lens, how expensive the materials used and the quality control used. If every lens is checked for optical and mechanical performance at several steps in the manufacturing process that adds a lot of cost compared to setting up a manufacturing line and sampling the occasional unit.
As you get a way from normal lens sizes, like 30 mm on a APS-C or 50mm on a FF then lens designs get more complex, longer zoom ranges also are more complex, larger apertures are more complex and require larger pieces of glass. The area the lens has to cover is also a consideration, a cell phone lens covers a very small image circle compared to a FF lens or medium format lens.
The 16-85 is both wider and longer than the normal kit lens at 18-55, this makes it more expensive, there is also the issue that many fewer are made so the parts used in it are going to cost more to manufacture. The manufacture may also use more quality control on non-kit lenses.
35 f/1.8 is a normal lens is made in reasonable quantities so is not going to be real expensive for APS-C, the same lenses for FF bodies tend to be more expensive. The 28 f/1.8 is potentially not real expensive to make on a APS-C camera but is harder to make for a FF. The market for 28mm APS-C lenses is pretty small as most kit lenses are not much slower at this focal length and have decent quality.
The final determination is what does the company think they can get people to buy the lens at. There are development and manufacturing costs for a lens, the profit on a lens has to cover this. This is also why older lenses are replaced with much more expensive lenses sometimes, the development costs were paid for long ago on the old lenses but need to be paid for on the new ones.
Modern lens development and manufacturing systems can reduce costs of lenses and we have seen some really good reasonably priced lenses lately. As long as the companies think they can sell enough of a particular design, that is not unreasonably complex or expensive to manufacture the prices can be pretty fair. So you can see a good cheap 35 f/1.8, but your are unlikely to see a good cheap 200 f/2.