1. Well, if you read the top of the post, the value of playtesting at the big game companies listed is why. I'm willing to bet that maybe 1% of people in this community have this experience with playtesting at those companies. In addition, I have multiple gameplay videos from the independent studios that I have done this for.
2. I researched the market and have done this for a while. The research shows that this community doesn't like to pay for much, (if anything). This point is specifically proven by your words. " It isn't cheaper to just go to a game dev community and ask feedback there?" Also, I'm not sure if it's "cheaper" as it may be free to do so. $30 is a dollar a minute for the half hour of gameplay. The price I chose is my way of trying to help the smaller developers that are serious about growing and truly want quality feedback, QA, playtesting etc. They may not be able to afford the higher prices If they spent money on contractors (i.e. art, music, maybe programming etc.) to make their game better, there may not be much left in the budget.
3. Again, if you read the post, in the testimonials, the value the other devs are shown. So, that answers your question there.
4. I even offered to play games for 10 minutes as "demo". Literally, a zero risk. Maybe you missed reading that too.
Bottom line: Instead of wasting your energy to respond the way that you have, you can take the time read and comprehend if the service is for you or not. If it isn't, you can kindly move on and say nothing.