Not really. Even then you'll get criticism that the teams were more skilled in one language, or that they didn't use the best practices of the other language. Also, even if you could manage to normalize for all these variables. You're still only going to be comparing the cost to create the project. You're never going to get someone to maintain the two projects side-by-side for years and compare the total maintenance costs. That is where the biggest benefit of languages like Haskell comes.

The fact of the matter is there never will be absolute proof of these questions. The naysayers will always have straws to grasp at.

I'm not sure what you're getting at. He's saying Haskell's type safety makes impossible the bug that was in his JavaScript project. As far as I can tell, it's impossible to write a type safe system in pure JavaScript.

edit: To clarify this thought a bit, obviously you can transpile code in a type safe language to JavaScript. At the abstraction level of the code written, the project is type safe. The generated JavaScript itself is not; however this isn't a problem if the transpiler is correct. The same principle applies to Haskell compiling to non-typesafe machine code.