One thing that may have been missed here: The reward pool is limited. That amount of money is fixed for each block that is produced.
It means that the current correlation of 1M SP to 100$ vote value is only valid in today's environment, with today's distribution of SP among the current users.
When you add more users and more SP to the mix, it will require more than 1M SP to get a 100$ vote.
At least, that's how I understand the workings of this platform. I leave this on the table for further discussion and comments...