Actually, I only have $12 worth of SP; that equals to an upvote worth about $0.003.

At the current price of STEEM, you'd need about $4000 worth of SP to give a $1 upvote. The average person on steemit has about 98 cents worth of SP. That means you need about 4000 votes from the average user to get a $1 upvote. Or you need to get lucky and hope some one with heavy investments into STEEM starts voting for you.