Data about ROI
With 50 pages on Google index starts to make about 50 cents of advertising a day, which says that each page generates a estimate of 1 cent a day with the actual visits.  (80 /dia)

Following this estimations I estimate that when the index rounds 500, I will be generating $5 a day in Adsense.
Sources
Pages “site:*****.** delicious” 50 and growing, now with “no-follow” links so they don’t take me out of the index.
14 days of Analytics after the traffic falled, with 1471 visits in 2 weeks.