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Actually in theory it is possible, Steemit owns a lot of SP that can be used to reward proper use of Steemit instead of purely selfish use. that way everyone can theoretically win and get more than a 10x self-upvote back. That's just theory though

Is Steemit now using all that SP for self upvotes?

But even then if you win some, someone else will lose some. There is no concept where money is for free.