Apparently, some shoes sold online, are for very specific lots (sizes and colors)  i.e.  that 11 looks like a great value, but bumping the size to 11.5 may show 'not avail' or drastically raise the price.  (kind of like the "Loss-leader advertising" done by car dealers.

In my case the shoes were 1/2  size too small. They looked ok, but I had to send them back for a larger size,  from 11 to 11.5  which raised the price $30 ! .  Maybe THAT's why they run 'small'.

This just in-  10 days later, the larger 11.5 size is back down to the original price for the size 11.  I guess one has to play 'stock market' and check prices (for YOUR size & color)  daily.

My Conclusion - Buying shoes online is very risky, as sizing standards have gone out the window.  Remember those slider gizmos that gave your shoe size?  Forget about them!  If you like a $120 dollar shoe (Nike, Reebok, ASICS - ymmv) and then decide on a different make (or even color/model of the same brand!). Better try it on.  Don't expect a size 10 of one, to be the same as a '10' in a different model. (this from an established shoe salesman.)