the short version is this..
The fed reserve can value or devalue the dollar any time they please by printing more or less of them. The real value of the dollar is virutally nothing as they only hold a small percentage of assets to back up the dollar in reserve. Banks are also only required to hold a small percentage of assets to back up the dollar. So, the real value in gold of a dollar is nothing.
It's an interesting video if you have the time and the bandwidth to watch it.