I believe Ames uses a graduated shipping fee schedule based on item prices. It makes it a bit more painful when just buying small parts, but when you think about the logistics of processing and order, pulling one-off parts, packing and shipping them out, the small parts order take just as much labor as larger orders.
Best bet is to call them if ordering oversize items. They can often combine two or more oversize items in the same box and only charge you a 1x oversize fee.
'67 GTO/Signet Gold over Parchment/Pontiac Built