Lmaooooooo, nice catch.
Another interesting fact:
-With Sanji instead of Zoro it would be 1.5b the total of their bounties = Luffy's
-With Sanji instead of Killer it would be 1.62b > Luffy's
Conclusion. With Sanji there, the four of them would be equal or outshine Luffy.
Think about it, Zoro can't move for himself in midair and he even failed a slash against a hundreds of meters long snake, can you imagine it from Sanji this?
Now we know why he wasn't being brought here.
Another interesting fact:
-With Sanji instead of Zoro it would be 1.5b the total of their bounties = Luffy's
-With Sanji instead of Killer it would be 1.62b > Luffy's
Conclusion. With Sanji there, the four of them would be equal or outshine Luffy.
Think about it, Zoro can't move for himself in midair and he even failed a slash against a hundreds of meters long snake, can you imagine it from Sanji this?

Now we know why he wasn't being brought here.