What are the main parameters from which the lens of SLR camera is expensive and cheap?

the most important parameter is the price! Ha ha.

But the above is not a joke, because there are too many factors, and market factors such as short-term speculation and international exchange rate changes have great influence.

Let's talk about something simple. The following is just a personal summary, which basically can't withstand any scrutiny. Let's gather together or have a look.

let's talk about the fixed-focus lens first, which is easy to sum up. The larger the aperture is, the more expensive it is. The header with the same aperture is the cheapest, and the wider or longer the focal length is, the more expensive it is. Fisheye in wide-angle head is cheaper than wide-angle head.

let's talk about zoom, which is a little more troublesome. In short, the constant 2.8 aperture is more expensive than the unstable one, and the constant 4 aperture may be similar to the unstable one, but it must be cheaper than the 2.8 one. Wide-angle zoom and telephoto zoom are more expensive than standard zoom (the same grade as mentioned above), and the zoom ratio is generally high in cost performance (just that the focal length covers a wide range, but the total price is not high and the imaging is poor).

generally speaking, the full head is more expensive than the dx frame head, the one with large front aperture is more expensive, the automatic one is more expensive than the manual one (there are many exceptions in this one, but it is generally effective when all other specifications are the same), the new technology such as shake release is more expensive, and the special lens such as ultra-low dispersion lens, fluorite lens or aspheric surface is used, the more you use it, the more expensive it is. Metal mirrors are generally more expensive than plastic mirrors.

the most important one: the heavier the lens, the more expensive it is. Some people have counted the price and weight ratio of several top-level lenses, and found that the unit weight price of each of their own top-level lenses is basically the same (second-hand 92 new price statistics, excluding speculation factors). In fact, another statistic shows that generally speaking, the imaging level of a lens is positively related to its unit weight price (not necessarily linear, because the imaging level can't be completely quantified and counted, and mtf doesn't mean everything)

In fact, the overall price of a lens is like this. The more advanced the positioning, the more expensive the design, and the more difficult the lens is to produce. Then there are the following types of advanced positioning: large aperture fixed focus, constant large aperture zoom, and top-class. There are several kinds of design difficulties: ultra-wide-angle, ultra-telephoto and shift-axis lens. There are the following kinds of lenses that are difficult to produce: large-caliber lenses, special lenses (including ultra-low dispersion, fluorite, aspheric surface, special coating, manual fine grinding and so on).

Generally speaking, the most expensive lenses should be: shift-axis macro lens (macro, shift-axis, special lens), large aperture super telephoto lens (large aperture fixed focus, large aperture, special lens) and super wide angle lens (super wide angle, special lens). There is also the more lenses of the same grade, the more expensive they are.

almost, it's not perfect. In fact, the simplest rule of lens pricing is that the more cattle, the more expensive.