If the Penguins buyout Fleury, they'd only have $2 million to spend on a backup to equal the price of Niemi. That $1.916 million cap hit is a penalty for 4 years too. Even if the Penguins retain $1 million of Fleury's contract, they come out at +$750k for next year, +$4.75 million after Niemi leaves as a UFA and $5.75 million after 18-19. If they buyout Fleury, they come out at +$3.834 million over the next 2 years and then go -$1.916 million over the 2 years after that, both of which while needing a backup.
I'm curious, but why is buying out Fleury even an option? Surely he gets traded or at worse, picked up by Vegas in the expansion draft.