From a material stand point it is interesting to look at what a dollar purchased less than 100 years ago in the United States. There are few different ways to look at change in material value. Comparing the cost of a cup of coffee in the 1930's to today, is very different from comparing the ratio of economic "impact" to build the Hoover Dam to today's costs.
The Hoover Dam was priced at ~$49 Million during the time it was built. To understand what that sounded like to citizens of the day, it would be as if the president announced a single stimulus project for ~$8,340 Million ($8.34 Billion) this month.
The following website has a nice calculator and some decent explanations that explain the different ways our dollar has changed over the years.