In the same section, he goes on to expand upon this claim with the following:
The real estate value of Tokyo, the received wisdom had it, was greater than the real estate value of the entire United States plus the asset value of every company listed on the New York Stock Exchange. The value of the Imperial Palace alone, about ten acres in downtown Tokyo, was greater than that of the entire state of California. Spurred by the overcentralizing of government bureaucracies and buildings in Tokyo and the city's strict tenants' rights laws, prices in good neighborhoods doubled every three years -- every two years in the prime Marunouchi or Akasaka neighborhoods, if you were lucky enough to find someone willing to sell.
...
As real estate soared, investors took out cheap loans, using the endlessly escalating value of their properties as collateral, and bought into the rising stock market. Capital thus generated blew back into the real estate market. ... "Only idiots and foreigners didn't get rich during the bubble," an equity warrants salesman for Japan's largest securities house once confided to me.
This book is a very sexed-up, tantalizing expose published at a time where its main marketing appeal was a peek into an exotic, orientalized, slightly menacing foreign land that had for a brief blip seemed poised to economically dominate the world -- but Greenfield did put the leg work in gathering interesting true stories and he does come off as educated and authoritative.
How exaggerated, if at all, is this characterization and contextualizing of the late eighties bubble economy in Tokyo?
This is a claim I've seen in many places, and I can't seem to find a reputable source for this information. Wealth in general (and the value of housing stock is a value of wealth) is a notoriously tricky thing to measure, and I see bad comparisons of wealth all he time. Between 1980 and 1990 the average housing price doubled. Commercial real estate tripled in value in Tokyo, and residential real estate grew 250%. Some neighborhoods probably did see the types of spectacular housing price increases mentioned here, but general rates were much slower. Moreover, if you measure housing prices against the rapid growth in incomes, the bubble becomes even smaller. There were real causes for land prices to soar, including sharp appreciation of the Yen, major capital inflows and rapid growth. One thing to keep in mind is that Japan actually has a much more laissez faire land market than the US for better or for worse. The rapid growth of housing prices meant that supply responded, more houses were built, and prices fell back to ground.
That said, at least in nominal terms, Tokyo probably did have the greatest concentration of wealth in the world. Tokyo is the largest metropolitan area in the world, and had a population of 34,000,000 at the time and more than double that of the largest city in the developed world at the time. Japan's nominal GDP per capita was $45,000, as compared to $28,000 for the US at the time, based on the flawed assumption that Japan could continue it's rapid labor productivity growth indefinitely. In dollar terms, I strongly suspect that Tokyo at the time had more billionaires than anywhere else, although actually getting a real measure for this would be really tough.
https://www.economist.com/blogs/graphicdetail/2017/03/daily-chart-6
Asia's Financial Crisis and the Role of Real Estate, By Koichi Mera
Building world city Tokyo: Globalization and conflict over urban space , Andre´ Sorensen
The idea that land of the Imperial Palace was "worth more than all of California" is one of those claims that gets frequently repeated in the press and less-scholarly books but almost certainly isn't true (it first appeared in an 1988 article of the Economist).
The claim derives from the record-high sales price for a small unit in a building in Tokyo's most expensive neighborhood during the bubble. Supposedly, if the per square foot price of that unit was applied to the Imperial Palace, it would be worth more than California. We have no idea what number was used for the value of California, but I think the key thing here is that it was used as a rhetorical device, not an actual serious claim. That unit's value could not actually be applied to the Imperial Palace.