Your answer likely lies in two areas.
First, the numbers of airplanes built. How many 182's were built in the 1960's and how many are built in 2010? Production economics.
Second, there may be union issues with factory workers. The existence of the unions has been one of the primary factors in the old-school Detroit American car makers no longer having the lion's share of the market. If there is a union that is involved at the Cessna plant, it might be a contributor.
All that being said, the new crop of light sport airplanes are all $80-150K. Cessna's 182 has already paid for its development, tooling, production jugs, etc. etc. long ago... so you would think that Cessna could make a 182 as cheaply as a Czecholslovakian LSA plastic airplane they just tooled up for three years ago?
If aircraft had followed suite, somewhere around 10 grand would buy a loaded 182!