I was 20 when I got mine pierced, and even though I thought my parents probably would've flipped if I had mentioned it to them, I went ahead and did it anyway. It cost me about $40. One day, several months after I had it done, I asked my mom what she would think if I got my belly button pierced. She just sort of waffled and said she didn't think I would ever do that because I hate needles, so I couldn't resist--I just lifted my shirt and showed her.
She didn't freak out, though...she just laughed and said I was nuts, and then she added that if that had been "the thing" back when she was my age she probably would've done it too.