Reply to your questions:
1. I purchased short, medium and long wigs. I particularly liked the long one because I styled that thing like it was my own hair.
2. Every wig that I have people tell me that they look very natural on me. They have many now with the yaki hair although synthetic, it closely reassembles our hair.
3. I paid anywhere from 25-35.00 for my wigs. I always purchased synthetic.
4. I really didn't care for it that much. I would wear them and when they seemly started to look worn, i purchased another. I figure I was saving money anyway because if i paid 30.00 for it and it lasted two months, that is a bargain.
5. I got the usual growth, 1 inch a month, but that is because you're doing the right things to make your hair grow, i.e., eating healthy, taking supplements, combing/brushing gently, etc. I wore wigs for a twofold purpose, i couldn't style my natural hair in a protective style that I liked, and the second reason was it was so easy to slap on that wig.
5. My hairline is very good. In fact due to the Crown and Glory method, my hairline is growing beautifully. I have baby hair all over.
6. Again the health of your hair improves if you follow a hair care regime. Find a program that works for you and stick with it. Your hair will respond if you give it the TLC that our hair needs. I don't think the wig per se contributes to that. I believe, and correct me if I'm wrong you need to do good by your hair and your hair will show it appreciates it by responding with long, strong, and healthy hair. That is what I'm trying to achieve. Hope this helps.