Most people who buy those sites dont make a cent. How are you making $4/day, where is the traffic coming from? As someone said, thats nothing to complain about.
When I started off I bought one of those sites too.. it made me like $5 in a few months time.. Waste of money imo
Kastro Are you writing your blog content yourself? I ran a Copyscape check and if its your content then there seems to be a lot of people pinching it