In the sci-fi movie Inception by Christopher Nolan, in the first level of dreaming, they kidnap Cilian Murphy and Tom Hardy tries to get some information from him, by impersonating Browning, his uncle.

Then they sedate him in a car. Tom Hardy removes the bag from his head, gets down from the car, and says to Di Caprio's character:

That boy's relationship with his father is even worse than we imagined.

To which Joseph Gordon Levitt's character replies,

This helps us how?

Is this a correct sentence? Why didn't he say

How does this help us?