Who says that the players are making the most impact at all? What if we scrap that thinking and entertain an entirely different idea:
For the ingame economy, each player is just as insignificant as any NPC.
The economy must also simulate NPCs never seen by any player, for example when no one is around a space station, it must still receive and send out cargo transports.
This simulation is likely done by merely crunching the numbers, no actual ships simulated flying around until someone enters the area.
The game can freely scale up this kind of number-crunching simulation in the background to more realistic numbers beyond that which players see ingame. Instancing already means that no player will ever be able to sit at a station and count the ships going in and out for anything beyond their instance.
And here comes the important part:
The background simulation takes into account the trade routes players are running, and adds the most efficient ones to its own NPC simulation.
As a result, player action does matter. If many players keep hauling good X from A to B and good Y back from B to A, the simulation will see that and simulate NPCs running the same hauls, as many as are necessary to turn this into a visible effect on the economy.
And as a final step, design-time performance optimization condenses this into an automatic, dynamic factor for any player-run cargo haul, how many hidden NPCs do the same one. They are never simulated individually, but in bulk as a mere multiplicator on the economic impact of a single player.
Now we have gone full circle and just let players have a bigger impact than NPCs.
