I think higher value of STEEM is more important in determining the amount of rewards an author gets as it determines the payout value of a post.
Correct. A higher STEEM price makes the $ value next to the post go up. With the changes to the UI it's now also easy to see that with a higher STEEM price more SBD's are created.
I just got a tool from a frien here to show how this works based on steem feed
https://www.steemnow.com/@josteem