As you can see from the chart, the inflation adjusted price of gold peaked just shy of $9,000/oz using the 1980 CPI formula. If you were to use today's CPI formula from the US Bureau of Labor Statistics, then the inflation-adjust price of gold in 1980 peaked around $2,400/oz. Does it make sense now why "they" have been tinkering with the inflation formula?
In 1980, the rise in gold price was largely due to supply and demand from western nations as many Asian countries, particularly China, had not yet opened up their economies. I would argue that today's macro environment is much more favorable for gold as China, India, Russia, and others have been overtly (and covertly) accumulating massive amounts of gold over the past five years.
So now take a look at today's price of gold - it sits right at $1,310/oz. If you believe, as I do, that today's environment is even more "gold-friendly" than back in 1980, then it makes no sense for the price of gold to be where it is currently. How many other commodities are still trading at a fraction of their inflation-adjusted highs?
Bottom line, regardless of which CPI formula you use, gold seems hugely undervalued at its current price.