It's hard to appraise a site..
Need to know a bit more about the monthly income, how long has it been running, where does it get it's traffic from (Search engines, or expensive advertising?? (only 20 links in google and PR3?!))
At least 6 times the average monthly income is an ok price for a site (IMO).
16,000 uniques pr day is very good, and if this an average daily number (over a few months) I belive this one must be worth at least low $xx,xxx