In other words, you won't get rich trying to mine bitcoin or other cryptocurrencies from your home. Because if there's money to be made, many others will jump in. To get rich, you'd need some advantage, like incredibly low cost of power.
Back in the bad old days of only-just-emerging bitcoin ASICs, the equilibrium was distorted by the long lead times for new parts and relatively few suppliers. (For all I know, this might still be the case with new algorithms/new manufacturing process/ASIC generation).<p>Another interesting thing to consider is that rational miners will often consider applying their hashing power to the coin whose reward/block time/difficulty/exchange rate factor provides the best return (among those that share a PoW).