> However if you grab the book yourself from the physical store and save them a step

The average customer gettibg the book themselves rather than ordering it and picking up at the counter is imposing more cost (and that's even more true of the average in-store customer, who probably hasn't searched online for a particular title and checked inventory and then decided not to do online purchase and pickup; by doing that you are making yourself indistinguishable, from a pricing policy perspective, from a much more expensive to serve class of customer.)