This may seem off topic , but to clarify what a trade deal entails: The SK president goes to SA to sign a trade deal so their corporations such as LG, samsung, Hyundai and the like can export and sell products in SA in exchange for oil and money. The economy of their country is based on manufacturing, however entertainment companies are also corporations selling products in the form of kpop. Big$hit, SM JYP etc make millions from album sales, tours, merch and events and SA is another market where a lot of $$$ can be made because the Saudis pay very handsomely. They have hundreds of employees and must pay tax all of this contributes to the overall economy of their country. Of course there is a political aspect to it, it increases their soft power (although if you ask me the kpop industry is highly americanized, main difference is race and langauge) but regardless has secondary effects such as increasing tourism, meaning more $$$. For the Saudis as I previously mentioned it means an attempt to improve their international image, divert attention from existing international crises and welcoming foreign investments as a ”free society”. So yes both aspects exist. I don’t if hosting the concert in their capital has a political significnace per se, it is their most populous city with the most wealth, hence it cam attract the biggest audience.I think you are right. Kpop has always been a political soft power tool, both in Korea and outside. They are bringing albums for the children of foreign politicians (f.e. BT$ for a Moroccan minister, EXO for President Trump). Bangt4n is their most powerful band abroad. By sending them to SA and to Riyyad rather than Jeddah, Korea is making clear that this is political rather than an ordinary run-of-the-mill concert. I doubt that the korean government will make money off the concert directly though. It is more a sign of goodwill to strengthen the bonds between their countries after the successful trade deal. I am sure we will see a lot of government officials at their concert, maybe even pictures from "private official" meetings with members of the royal family.
This whole rant made me once again realize that these kpop groups are nothing but manufactured groups run by corporations with little individuality. At the end of the day they and their companies are all after money