1. Wow, you can make serious money selling your hair.
2. It took her four years to do, so that's only a bit over $250 per year. Not the greatest, but if you like long hair anyway, why not?
3. She really marketed her hair well. Notice all the great selling points she lists.
My wife grew her hair out one time for a charity and it was a nightmare. For months she simply had long, straight hair that wouldn't do anything but hang like a limp towel. It was like I was married to a hippie gal from the 60's. But it was for a good cause (charity), so I dealt with it. Once. That said, if you like the way your hair looks when it's very long, why not grow it out and sell it?
And if you want a few more ideas for making some extra money, check out 11 Great Ways to Earn More Money.