Only formal "you". "Sie" is capitalized, so it means "you".
The other reason it was probably not accepted is this linguistics thing called pragmatics. Pragmatics takes into account how you say something, not just the literal grammar and such. In English, the "pragmatic" way you would say this is "You will / You'll pay for that". "Therefore/ for that, you will pay" can be used, but only after explaining the reason why someone should/will pay for it. It would never be said as a stand-alone phrase without an explanation.