Looking at two Canon L lenses they had one cheaper than and one dearer than the rest.
That's the way retailing works. It's almost impossible to be cheaper on everything
. The retailer gets the best discounts on the big volume sellers, so there's always items they'll be cheaper on, and others they are less competitive on.
With items like the L series glass, there are some big sellers like the 24-105, 17-40, 70-200 and some ( 400mm f2.8 ) they might not sell more than a single unit a year, if ever.
Edited to loose stupid emoticon