I am interested to see research on the development of transportation costs over the centuries. I realize the difficulty with researching this topic so I am interested in anything, which can enlighten me on the subject. The research will possibly be focused on types of transportation like over-land transportation, passenger transportation, transportation of letters and so on. The important thing is that the research enables a quantitative comparison over several hundred years. The research should show the impact of innovations and building of infrastructure so I can develop an understanding of the impact these these have had.
Tim Blanning The Pursuit of Glory has a whole chapter dedicated to this covering Europe between 1648 and 1815. It covers costs, travel times, and road availability as well as water ways.
However, that is just a narrow part in time and local.