This Seeking Tech guide will show you the best farming spot near Martira in Metaphor.
Use the following video as a reference:
For the first step, make your way to the save point in the Abandoned Tomb. Next, you need to make your way to a cluster of enemies on the southeast side of the map.
There is a level 25 enemy along the way that you can take out if you are level 28. Otherwise, you can easily run past him.
This group of enemies has a maximum level of 11, so you should be able to defeat them in the overworld. If you have the Merchant Archetype equipped, then you will be able to earn around 7.5 K per run.
After defeating them, use the save point to go to Akademia to respawn the same enemies. If you keep doing this for an hour, then you could end up earning more than 500K.