There are a couple of factors:

• The price fluctuates as the value of the steem currency changes
• A portion of what you see there goes to pay for comments and votes

The comments and votes do not TAKE money from you. They are included in the estimated value. So without those comments and votes your value would be less. In fact, more comments that attracts interest and high value votes increases the chance you will make more.

When it cashes out it locks the price relative to the steem currency value at the time and after paying out the comments, and votes (curators).

At least that is how I think it works... anyone feel free to correct me.