Maybe I'm not the only one who has noticed this phenomenon but after you publish a post on Steemit it slowly losses value until the post pays out rewards. Have you ever wondered why? Well, it's a two-fold issue.
The first part of this occurrence is that the rewards you receive are related to the price of Steem. As the price fluctuates along with other cryptocurrencies in real time you can earn more or less of a reward by the time you cash out. This is updated on your posts as people upvote them, and large fluctuations in price can actually result in your payout dropping when someone upvotes your post.
Secondly, when your post is upvoted, the upvote given is shared with other upvotes through the voters VP. As the voter upvotes other posts their VP is diluted and the potential post rewards you receive can drop along with the dilution.
Hopefully this helps clear up the inner workings of Steemit for those of you who may not know about this phenomenonn.