Switzerland is also a small, homogenous society with a population of 8 million people and 3% unemployment. They make a LOT of their money from their banking laws (i.e. Swiss bank accounts for people trying to hide their assets). They have the size and the excess money to do this.
Throw 300 million people into Switzerland with no jobs and a huge welfare system, and it wouldn't work. But it works for them.
Their GDP is 632 billion / 8 million people = a per capita income of $80,000 per person. Since 1.5 million people are under 18, the adjusted per capita income is more like 632b/6.5m or $100,000 per year.
Not to mention the assload of excess cash Swtizerland has saved up from basically winning the lottery after WWII.