I say "NO! To nearly limitless credits"

The price of durantium at the Galactic Bazaar is floored to 10 credits. When trading with a civilisation that has an abundance of durantium it values each unit at much less than 10 credits. So if you're short of credits, buy durantium at less than 10 credits per unit from that civilisation (or trade tech) then hammer the sell button over the durantium icon at the Galactic Bazaar to short out the cashflow problem.

I think the above is indicative of a bug in the economy model, and while I shoudn't give in to the temptation to exploit it, if it's a choice between surrendering the game after 70 hours gameplay, or leveraging the bug, I'm afraid I'm only human. Leveraging the bug it is then!

So I think either:

1. Remove the price floor at the Galactic Bazaar or
2. Ensure civilisations don't trade resources for less than the floored value at the Galactic Bazaar.