There are a lot of factors that go in to how much a post pays out. Having spent a lot of time gaining a following is probably one of the biggest factors. Who is following you makes a big difference too. (One upvote from one of the top SP holders will add more to your total than hundreds of votes from 'regular' users.)

The quality of your posts makes a big difference too. Whatever you write needs to justify whatever upvotes it will ultimately earn. The topic needs to be interesting, the subject and thumbnail need to capture attention, the post needs to read well and keep the reader's attention. Most importantly, the reader needs to feel at the end that they got something of value by reading your post.

If you do all of that, and you do it consistently over a period of time, then you will slowly build your reputation and gain more followers. This will lead to higher rewards for your posts in the end.