Tuesday, September 20, 2011
According to this advertising flyer from 1979, the AD&D Monster Manual and Players' Handbook hardbacks, as well as the Holmes boxed set and other boxed sets were priced at about $10, while the supplements for the D&D boxed set and the adventure modules were about $5. According to the CPI Inflation Calculator, those are approximately equal to $30 and $15, respectively, in 2011 dollars. If I recall correctly, the Dungeon Master's Guide cost $12, which would be about $37.50 today.
So, in today's dollars, the original AD&D set of books would have run about $97.50, for about 470 pages of material that we're still mining to this day.