At best case for Haskell, 15.5 times slower. The thing about bounds checking, in Haskell it's always there. In C, you might have it, you might not there is no certainty by the language, only by design and implementation. So with C, one is free to live dangerously.

If you're using GHC, there's Data.Array.Base.unsafeAt which is the one which doesn't do bounds checking.