Note: The Tomb Kings are the only faction that use resources for their mortuary cult mechanic (Edit: A similar mechanic called forging has only been added for dwarves in Warhammer 2 since it originally posted this answer). For all other groups, resources only increase the value of trade agreements. They are therefore generally right to think that these resources are not actually used by the trading partner, but not in this particular example. Nor have I ever seen evidence that more trade resources increase the likelihood that someone will agree to a trade deal. The diplomatic system here is very veiled. I have seen that political groups with +200 connections oppose profitable trade for them and political groups with +5 relationships accept the same trade. In the next tab, the business details are displayed. If you have a trade agreement with another country, here is a list of imported and exported resources and their prices. Importing construction resources is very important in later phases of the game, if the larger structures available do not require easily accessible resources like marble. On the left (your page), the user interface shows you how much money you make from trading and what resources you export to your trading partner. The right side shows how much money they make and what resources you import from them.
In campaign mode, it is possible to act between two political groups. Trade deals can be concluded on the diplomatic screen, allowing political groups to exchange trade resources and generate additional revenue for both groups. Beastmen, Greenskin and Warriors of Chaos factions cannot act. The Empire`s income comes from a variety of sources. The most important taxes are levied on the entire population, and just behind it, you have trade. The income from slavery depends heavily on the number of slaves you enslaved during your conquests (this is a simple multiplier of basic income in the provinces). In addition, you can receive an annual tribute from conquered nations and rewards for the accomplishment of the mission ordered by the Senate. In your example, you earn 620 gold per spin and no resources, while Arkhan earns 110 gold and all those resources on your end.
Think of it as “I make so much money to export this and that”. . . .