Trying to find a theme for a new mechanism for my game Meeplesburg

Looking for some advice on theming a new mechanism in my game, Meeplesburg.

The game board is a map of a city laid out in a 5x5 grid. Players build buildings by placing a building tile on a square, then place a wooden house of their color on it to indicate its theirs. At the end of the game players will receive 1 victory point for each building by itself, and 3 VPs for each building in their largest contiguous group.

The new rule is that when you are putting down a new building tile, if it is adjacent to another one you own, then you gotta pay for it! When I put a building tile down on the map board, and it is not adjacent to own I already own, then I can put it down for free. But if it is next to one I do own (orthogonal), the it will cost me $1 to do so. If I put one down and it creates a clump of 3 adjacent buildings I own, then this will cost me $2, and so on and so on.

I love this mechanic, but now I need to create a theme for its existence in the game.

Here some ideas. Let me know which one is best or if you can come up with one that is better.

Builders Guild Fee

We could say that each player belongs to the Builders Guild, and they have to pay a fee when they build a property next to a property they already own. Perhaps the Guild likes builders to spread out throughout the city when they build and charge you a fee to dissuade you bunching up.

King's Taxes

King Meep (king of the meeples, don't cha know) wants his new capital city of Meeplesburg to spread out and have lots of variety in the various districts. If a player is constructing buildings next to ones he already owns, then the King is charging property taxes.

These ideas for theme are very satisfying to me, but maybe I just need to improve the wording. I really like the mechanism, so I want to find a way to make it work with the game.

Thoughts?