I hardly think that paying for AWS or any other servers or amassing the technical skills necessary to mine (in whatever way that is possible) comes at no cost ... In fact, it's quite risky as there is no known market at the time and the entire venture is speculative, and, as such, those people are securing the blockchain at a potential loss.
And can you define 'a lot' -- maybe in terms of percentages? Is this more than 5% but less than 15% (combined)?
Also, what happens if someone decides to purchase STEEM at these low prices (or possibly even lower ones) and becomes vocal (meaning, they decide to do what they want with their stake) ? What's the difference between buying it and earning it from mining rewards?
RE: Whales upvoting chosen accounts crap for the rewards is one thing, attacking the rewards of a genuinely productive account is utter madness