You have to consider that the STEEM price linearly influences the values of votes on an article.
So the votes that contribute to a $100 article at a STEEM price of $4 would only suffice for $25 at a STEEM price of $1. Hence you would need way more votes to achieve $100 for an article.
Actually the amount of STEEM power rewarded for a post does not depend on the current price of STEEM at all. Only the STEEM power of the voters combined with the voting weight influences the amount of SP reward.
I think you misunderstood me, as I was talking about the article who would in its early stage after the publishing (up to max 48 hours) reach the amount of displayed reward of $100 while the Steem price would still be around $2 at the day 7 when its payment dues, and if in the meantime the Steem price increases to $4, it might show displayed reward of up to $200.
Regarding the Steem Power reward and how it's calculated from the total shown under our posts, unfortunately, you are wrong as the STEEM price is the only one that, in fact, influences and determines the amount which would be paid to us (from the total accumulated through different amounts of given upvotes).
To learn about it and find more in-depth explanations how our rewards are calculated you may check the following articles: