are you being ranked #1 for your primary keyword?
what is the avg money that a single sale brings on your site?
if you say, you are ranked #1, and you get a lot of money from this, then why are you arguing? focus on your core business instead of seo. in long run, you will be more profitable?
internet is full of books on how to do surgery, but would you try it yourself? seo is a ever evolving science, let someone whose main job is seo to worry about it.
p.s. I am not a seo guy. i run a business and decided that I want to do seo myself, because I enjoy it. It has become a hubby for me. so what I told you above goes against everything that I am doing myself. Again, the reason is that I enjoy it!