Originally posted by PollitowuzHere My less than useful knowledge on lens design doesn't understand it, but why is that good 85mm glass is so darn expensive??? The design by now should be quite easy to make, like a nifty fifty of sorts. Looking around for a good inexpensive 85mm, since my pockets aren't necessarily deep, being a high school student means extremely limited funds
First, good glass tends to be expensive.
For some reason, the 85mm focal length seems to be a fairly rare animal, there just aren't a lot of them out there.
The older Pentax ones (85/2, 85/1.8, etc) were never common, so their price is jacked up due to rarity. The faster ones (A*85/1.4 as an example) are rare and expensive hunks of glass, and now that it has it's truly well deserved cult status, it is valued even more highly.
Amateurs tend to buy zoom lenses, so they are getting the long end of a 28-80, or the short end of an 80-200 and are happy. Discerning amateurs and pros don't account for much of the market, and they are the ones who would be buying 85mm lenses.
Low demand = higher prices, since economies of scale don't occur on low volume manufacturing.