Ask HN: Whats an 'acceptable' Adsense traffic to ad revenue?

I run a website http://blacklis.com, which gets around 4000 uniques a month, its not a massive site but I enjoy running it.

I wanted to reach out to Adsense users of the world and ask what they believe is an acceptable Adsense traffic to ad revenue.

For example: My site gets 4000 uniques per month and earns on average $5-9 per month in Ad revenue.

It would be great to hear from someone, knowledgable in the subject :)