Thanks for the reply I thought along those lines myself. The price I guess could be it is bought in another country much less than the established price.
Maybe this is a good time to state I'm assuming you're located in the United States.
You might already know this, but just in case:
If the lens was bought in another country and imported into the U.S. by the merchant (B&H, Adorama, your local dealer, anyone, etc.) rather than the official importer (Canon USA), then that is known as "Grey Market". Like a refurbished lens, a Grey Market lens would be less than $3900, but not by as much - probably by only $50-200 (it is still a new lens). A Grey Market lens usually comes with an international warranty (rather than the "USA" warranty), and it would be clearly stated by B&H that you are buying such a lens. (Caution: not all merchants are so up-front about it.)
If you paid $3900 for your lens from B&H, you have a brand-new lens with a USA warranty that was imported by the official importer. No worries.