You should consider the page density (Internal Frag) in addition to the External Fragmentation. And the value to consider for internal frag depends on your data and page density settings. If you have not altered your fillfactor from the default and you have avg_page_space_used of 75% and 1000 pages, you have incurred about an extra 250 pages. If you then need to scan the table you can be looking at that much more processing that needs to be done.