I disagree about the transfer costs making Harberger tax unworkable, that gets priced into the self-assessed property value. You pay taxes on the use value of the property to you, not the market value, which is typically lower. When you want to sell, you’ll offer at the lower market rate.
But this actually points to an even larger problem. Harberger taxes as such would be incredibly destructive to communities. The stronger the community, the higher the use value, meaning the higher the self-assessed tax rate would have to be in order to reflect the worth to you. But the value from community is uncashable, meaning that there’s an unjust tax burden for having a better community. And people are usually only liquid to a minute proportion of the value of the intangible things in their lives.
Thus, people likely have to assess below their use value, which means the community can be eroded by compulsory sale and eviction. This already occurs in rent-paying communities, which are destroyed when property value goes up and they can no longer afford to rent there.
Tbh, you probably end up fighting this by having your neighbors in the community firebomb the property which got bought out from under you.
This isn’t a great way of thinking about intangible value, since most people are far less liquid than the value of the things in their lives. If your mom needs life-saving treatment for $10,000 and you can’t afford to pay it, does that mean your mom is really worth less than $10,000 to you? No—her existence might contribute hundreds of thousands of dollars of devotion, emotional support, and sage advice to you. It’s just that nobody will accept those things as collateral for a loan.
The Colosseum doesn’t have as stark a value proposition going for it, but by a similar argument it’s easy to imagine the public benefit of some building being greater than the amount of money that can be raised to support it. Personally, I think the Colosseum is mostly only valuable to the Italian state for the legitimacy that it buys it, a little self-justifying scheme of wasting taxpayer money to manufacture taxpayer assent.