All my lenses are used and you can get a pretty good idea of reasonable prices by monitoring the sold items either here or on fredmiranda. I got my 70-200 F4 on FM, and my 17-55 here, both for reasonable prices (close to the average sale price for a used copy of that type of lens). I got the 10-22 at the Canon Thanksgiving refurb sale. Getting a refurb from Canon is another good way to go if you can hit one of their sales. Usually, non-L lenses don't go out of stock the femtosecond after the sale starts, like L lenses do 

