Actually, I wrote my own tool for getting commodity prices from web sources combined with my own entries, not for getting the best prices in the whole universe, but just for saving some time and limit pen&paper work. Not sure if this can be taken also as cheating or not.

In any case it showed that writing down own data is much better and actualized option, at least during beta. I found some nice profits on my own that way, better or compared to which those web sources offered, and in close star systems.
Unless there will be some ship module as Avago-Earo mentioned, classic pen&paper method with pre-printed structured tables is probably best, fastest and fun way of trading. It may change if various webtools will be regularly updated across majority of star systems, but I doubt so.