There is a high competition for specialised hardware. When Bitcoin started, everyone could mine it on CPU, then GPU, then FPGA and now only an elite can afford the $10K ASIC. The production of the hardware is highly centralised and the people that have access to it are decreasing everyday.
That's partly because we are at a special time in Bitcoin history. It will mature fairly soon (over the next 5 years). ASICs will plateau in power as they catch up with mainstream chip technology. Then they won't be superseded so quickly, so they'll be kept longer. They'll be produced in greater quantities. They'll become cheaper. We'll go back to more people being miners.
How come ?
As time goes, it is getting more and more expensive to build the best ASIC chip.
It is getting harder and harder for new competitors to enter the manufacture market.
It is also getting worse for miners that have to take more and more risk.
Today, if you want to be competitive you have to make contract directly with the manufacturer, 6 months in advance and that require ordering over $200K - $1M.
Even with this, we see mining group going bankrupt (COGNITIVE).