I'd like to see a reference to millionaires who legally owned private property of that amount.
Legally owned? The USSR's nomenklatura lived quite well without benefit of legal title.
A joke going around about Leonid Brezhnev's mother, who was still alive when he rose to the top job, illustrates this confusion about communism and property:
Brezhnev's mother came to visit her son."This is my house," said Brezhnev, showing her around. "And this is my car. And that's my swimming pool. And this" — he shows her some photographs — "is my second house. And this is my airplane. And this is my villa on the Black Sea. And this is my yacht."
His mother gasps in wonder. "You do live well, Lyonechka," she says. "But I am nervous for you. What if the Bolsheviks come back?"
In fact, the Bolsheviks withered away as soon as their revolution succeeded. They were replaced by a totalitarian dictatorship which based its legitimacy on the myth of communism.
What was different in China was that the rulers figured out that communist central planning is not an effective way to organize an economy. They continued to call themselves communists, but in fact transitioned most of their economy to capitalism. In 1978, Deng Xiaoping invented "Socialism with Chinese Characteristics", which was actually market capitalism, with profit and loss and private enterprise. The reforms resulted in decades of 10 percent growth, transforming the country.
Optimists predicted the authoritarian regime would not withstand the changes brought about by such growth. However, the Party has proven to be quite adept at allowing economic freedom while brutally repressing whomever it feels threatened by.