There is a way of determining relative value by using a technique that my historian friends often employ. When doing economic research in the 18th and 19th centuries they use the annual salary of a clergyman as a measuring rod. Apparently that remained fairly constant in terms of buying power.
In the US we could use the salary of a member of congress; an Ivy-League professor; or a ship's captain as a metric. A working-man's income would be too regional and business-cycle dependent.
These kinds of embedded metrics do away with the more ambiguous calculations that MarkOue struggled with a few posts above.