As r0ach correctly pointed out, it is dynamic and there is always give and take. A particular marginal miner my drop out but another will take his place. Costs are always changing. Even political connections with a corrupt local official in China can disappear at a moments notice with one bullet. Nor does China have a monopoly on corruption, so cheap electricity appears elsewhere. The cycle continues.
This belies understanding that costs can't exceed income.
As the lowest cost producers scale up, they drive income to the level of their costs (thus no profit for any marginal miners). Otherwise they form an oligarchy to raise income (e.g. transaction fees), but then they can exclude the other miners.
The coinbase along with the price being driven by speculation is a short-term mitigating factor but that diminishes as the coin matures and becomes widely used. Then transaction fees dominate and coin exchange price becomes stable.
Sorry my QED was a strong one.
Also I think we were originally talking about the breadth of distribution of the coinbase, and 0.001% is even worse than a typical power law distribution of wealth. (Note Monero apparently has a CPU friendly hash and thus probably had better distribution percentage participation, but limited to those who know about mining it, which is unfortunately a very small number of people)
As you know, I am adamant about this, because I am intending to create a token that I believe can have very broad distribution and also defend against long-term centralization.