Even if power is free, you still get only a limited amount of it to turn into hashes. Power sources like plants or dams only produce so much. Even if you have b

Even if power is free, you still get only a limited amount of it to turn into hashes. Power sources like plants or dams only produce so much. Even if you have bribed a corrupt grid operator to give you 100% of the output from a X megawatt coal plant for free, you're still limited to X megawatts of hashing. If you can turn that X megawatts into 10*X megawatts' worth of your competitors' hashing, well, you just 10xed your profit.