Measuring wealth through documentary records is certainly more reliable than 
relying on artifact inventories, but has it's own peculiarities. A pass 
through the regional economic history literature could be helpful to provide 
an overview. I did an analysis of the pathways through which consumer 
artifacts pass in pre- and post-revolutionary Virginia, and there is great 
variation in those source paths, which is likely to be reflected in 
variation in consumer prices. The market area -- number of choices the 
consumer has to obtain hard goods -- is probably  one of the bigger factors, 
as well as the annual income cycle represented by the type of crops (for 
agricultural populations) and the scheduling of planting and harvest, and 
therefore the scheduling of disposable income.

This paper was published in the Archaeological Society of Virginia's Volume 
on Nineteenth Century Archaeology, available at the ASV website. These 
factors changed rapidly, but at different rates in different parts of the 
country, so a full grounding in local history is essential.

You have to think about whether you want to study the sociology and 
economics of the past, or something else. In the former case, all data must 
be fully utilized.

Tim Thompson