Alright so, I've been trading the event cargo for more than 2 hours straight and the only thing that I can say is - it's not worth at all.
If you want to promote Gallia and make people go there to trade the event cargo you need to give them profit. Let's be honest, what's 3500/unit? That's right, it's nothing, so in order to improve this event you will have to drastically increase the profit. There is risk of people getting caught, people like [ALG] let's say and if they get caught by GRP/GRN they're out of Gallia. Will the [ALG] risk such thing for only 3.500/unit? No, they won't.
I hope you get what I am trying to say and I hope that you will increase the profit. How much? I would leave that to you.