I like the data dumps. If you're new to json you can see it formatted on sites like http://jsonviewer.stack.hu/(no affiliation there). Load the URL to the specified file name in the "API" spec.
I'm not convinced that making the data available, or even available in real time would negatively impact game play. After all, you can just ask in the forums what "iron ore" is selling at in Kingston/Port Royal and someone will probably answer. Maybe not for every port but I guess that depends on numerous factors that beyond the scope of this thread. I don't see stats on how many players are sailing from port to port every day to check prices or if the requirement to do so in order to get updated prices affects the time they spend in the game. However, why not try? Doesn't that sort of thing fall in line with testing?
I'd like to see a real-time tool publishing the data from the database, or even in semi-real time like an update every 30 minutes and accessible via an easily coded open API like REST. If the server hit is, or becomes too much of a burden then data dumps could be made to a NoSql solution running on CUDA. You can process millions of records per second with a good GPU and not worry about performance as much as band width.
These data dumps are cool. Thanks for sharing.