grammar - Are these questions grammatically correct?

I have seen questions like

• "He went through all that just to go to Columbia?"
  or


• "That's the Ferrari?"

and I would like to know if they are grammatically correct.
Can you use questions like that in regular speech?
Can you even start a question with "you" or "that"?

Answer

These questions are grammatically correct. In written English, there is nothing wrong with indicating an interrogative solely by putting a question mark at the end. In spoken English, intonation is used for this purpose. There is no requirement that the interrogative mood be clearly expressed in the words used.

You can certainly start a question with "you" or "that". The easiest way is by eliding a word like "do", "did", "are", "is", or "can":

Omitting "do": You really expect to make out in that sardine can?
Omitting "did/does": That help?
Omitting "is": That what you were looking for?
Omitting "are": You sure?