Visit Zurich. Prices are ~2x what they are in my (fairly pricy already) area in the US. That's the direct consequence of high median income: businesses charge what the market will bear.
Note that the article is about wealth, not income.
The high price of the CHF also has something to do with it. I visited the French-speaking part of Switzerland a couple of summers ago (Geneva and Lausanne) and at some point during that visit I realized that those two cities (and the rest of the Swiss cities, of course) were among a very short list of European cities not directly affected by war in the last 200 years or so. Under these circumstances of course that everyone will be busy giving the Swiss their money and valuables for "safe keeping", which among other things translates into said high price for the CHF.
Did you mean the US is?
Depends whether you use median or mean. Switzerland is #1 by median, which is likewise not something I would have guessed.