Good question. Each day, the Steem reward pool is filled. We give a little of it to each other when we upvote each others' comments & posts. The richer the voter is, the larger the reward. That $0.30 is the reward given to you by my upvote on your comment. It doesn't come out of my pocket, but out of Steem's daily reward pool. As you can see, @gentlebot upvoted your last comment and because that user has more Steem/SteemDollars than I do, his/her vote was worth $3.52 of the reward pool.