I am sorry to tell you but you've got a big confusion about steem payout.
First of all, SBD price is pegged to $1, so is value will fluctuate around that price.
why are you making a conversion of the author SP payout using the median price?
The system do exactly that.
I suggest you to go study how steem payout works.
RE: [ENG]The psychology of investors applied to Steem. // [ITA] La psicologia dell'investitore applicata a Steem.