6.99 - for real or a scam?

After having played Democracy 2 and loved it, I browsed the site and saw Rock Legend. Played the demo and it seems fun. I was looking for reviews online when I saw it being sold for as little as $6.99 on a number of sites. This is just over a third of what it’s being offered for here. Can I buy from those sites or would I be supporting a scam?