From role play perspective, one could say, that you are just making good trades (e.g. buying low, selling high)
I see what you're saying, but this doesn't fit the model for arbitrage. Going long and buying low to sell high usually requires taking on some risk. In that case, the value may decrease over time. There is no risk in this scenario, I literally buy and sell straight-away.
Or perhaps as an intermediary I have contacts that aren't available to all which would allow me to re-sell at a marked-up price. This would make sense for standard trading between civilisations, but the Galactic Bazaar is available to all, non?
Anyway, thanks for forwarding this on, the above points are simply additional musing for the team.