You can use the word "see" at the beginning of a sentence for several different reasons. One is to contrast what you're going to say with what the last speaker said:

A: I'm not worried about saving for retirement. I figure it will work out somehow.

B: See, that's the difference between you and me. I can't just leave my future up to chance like that.

A: We should definitely go with the first option because it's cheaper.

B: See, I'm not so sure. It might be cheaper right now, but in the long run it's going to cost more to maintain.