This actually the part of high tier gaming that is fun. As a DM, I get to watch players creating the setting! They are doing the city-building, the world-building.
As a DM, think about how the city and the world respond. Encourage players to build stable institutions. Enjoy the worldbuilding as it happens in live time.
I agree with this wholeheartedly. In my homebrew campaign, I also take it one step further- anything "broken" I can think of that a high level player can do, someone in the game world could also have thought of, so I incorporate some of that into my own world building. For example, with a Wizard with access to 9th level spells, including Wish and Simulacrum, I'm sure folks have considered that they can have limitless duplicates of themselves. You create the Simulacrum, it wishes for a ruby worth enough to create a Simulacrum, and casts Simulacrum with you as the target, the new clone casts wish, etc etc. They can't replenish spell slots but nor does it cost you anything beyond the initial 1500GP expense, and there's no limit to how far the chain can go. The only "annoying" part is that while the original will follow your orders directly, you have to order it to order the second one to do something, and so on and so forth.
So in my world, a huge portion of the Guards and Laborers for a nation steeped in Magic are formed of 'tapped out' clones who have expended all their spell slots. The lore includes the idea that early on he would chain dispel them and start over, but he messed that up at one point and missed a link, resulting in a whole branch of them which does not respond to orders (directly or indirectly). They now have formed a secret society, the "Order of the Free Mind", dedicated to toppling the social structures of that nation. Since they can easily blend in with the 'legitimate' clones they're a real thorn in his side.
IMHO, take how 'broken' the world can be via high level magic and make it a Feature, not a bug! Think through some of the logical consequences of teleport circles and other high level effects and incorporate them in your game world, and when the players 'break' the world with their chicanery, have it live and breathe and respond to them, rather than saying 'no', and the world will be richer for it (not to mention your job is easier).