Intensionally tried to check out the price of the above domains and I came up with these stats.
But then am not sure how fare this is true?
F1
PR 0
f1.com was registered on: 06-Mar-1995
Domain Age: 1 decade 3 years 3 months 3 days
The total number of pages that contain links to: Google: 4,590
The estimated value of www f1 com is: $15,427
F4
PR O
f4.com was registered on: 17-Nov-1999
Domain Age: 8 years 6 months 3 weeks 1 day
The estimated value of f4 com is: $469