I think this is a good set of visuals and programming, but I think it would work better as part of a larger game. I'm reminded of yahtzee croshaw's old game "adventures in the galaxy of fantabulous wonderment", which had a similar trading system but less advanced (such as not having the neat orbiting destinations). One important difference is that one had plot and gameplay reasons for not just switching between two planets the whole time trading two goods. The fluctuations in price don't deter the strategy of just hogging one trade route and two goods. For example if there were only one planet to get each upgrade and one planet where fuel is cheap enough to be a good buy, that would encourage the player to plan out more complicated routes.
Other than that, the only problem I see is that having to click 30 times to fill or empty a level 2 cargo hold is tedious.