I started dancing at the Fairfax, VA Fred Astaire studio in May 2013,and my experience has been completely different then some of those described. Most of the students are in their 40s to 60s, some older and some younger. I would estimate that 3/4 are married and 1/4 are single. Most of us are professionals that work long hours. I would agree that it is expensive but it is the only activity I found where I can work 11-12 hours and still have the energy to dance. My instructor has been dancing since he was a child and has won numerous national and international competitions. He is not learning steps from videos the night before. When I joked with him that I was his favorite student, I got the "knock it off" look, so that was the end of that :) Do I enjoy dancing with a hot young stud with puppy dog eyes? Yes, I do. Do I have any illusions that he is "interested" in me? Absolutely not! One of the unexpected perks is that many of the students have formed friendships.
If you live in Northern VA, I highly recommend the Fairfax Fred Astaire studio.