I read your post again and actually we agree. Rewards are shown in USD (under each post) but paid out in SBD/STEEM. Your calculation is correct.
I just got the payout for a post that shows "Author reward $25" and I received 12.587 SBD for it. Which equals $25 USD.
Thanks for getting back and confirming from your personal experience. Finally! ✋
It was a good discussion which lead to more research and ascertained truth so thanks.