This article does an M.Zuiko PRO lens comparison with various Nikkor lenses. To arrive at the best comparisons that I could, the same apertures and equivalent fields-of-view were used where possible. All equivalent field-of-views noted are based on comparisons to a full frame camera format. Obviously there are not exact matches for all of the lenses between these two brands and formats. This is not a performance comparison. It is one based primarily on price, size, and weight.
One of the reasonably common comments expressed in online photography chat rooms is that Olympus M.Zuiko PRO lenses are ‘expensive’. This begs the question, “Compared to what?”