The economy in ED is awful.
I can take this part and nod a little in agreement. However economies are hard to model and for a game, in general, ED is mostly pretty good when compared to many other game economy simulations.
Basically what you're asking for is 'more credits' from your specific chosen task, even as others have pointed out you can make vastly more credits doing any number of other trade runs or even other activities.
The biggest problem in ED is everyone (and Frontier themselves agreed) wanted more credits to such an extent that over time (since game start when it was harder to amass wealth) making money has become kind of easy. As a newbie player i blasted through half a dozen starter ships (and a few internal upgrades on them) to get my Asp Explorer in about 15 hours of newbie (ie inefficient) game play. That is just because people complained they wanted more money, more easily, and Frontier agreed to those demands.
THAT nearly broke the game for me as a recent new player, so be careful what you wish for.
What i could suggest is that in whatever trade run you are looking to do, you can also check the mission boards and passenger boards to see if any of those also match up with a trade run you might consider, as that can add a nice overall credit increase just in case the profit from trade is not as good as hoped for.
What i'd like to see to better balance the glut of cash making, is a better risk/reward mechanic specifically around the cost of running a spaceship (higher usage of fuel and very specifically increased repair and maintenance costs) as you basically never have to worry about that as far as i can tell so far.