I just want to add that many factors may go into a company's shipping policy/fees. Whether a company decides to charge by dollar amount, weight, #of items, shipping method/carrier, or a combination of these, boils down to finding and implementing a process that works consistently for them.
They will have hard costs of boxes/ packaging, packing materials, labels, printer toner, warehouse storage space and of course labor before even getting to the actual shipping costs.
Labor is big and needs to be as streamlined as possible without risking errors. Some companies will double check items in the box to the order before it goes out the door. Restocking bins when more supplies are ordered also takes time.
Another consideration, as the buyer is, does the company consistently get your order right? And do they get the shipment out the door promptly?
These and customer support have value which equals $$.
When a company has free shipping, it has to be added into the price of the products. Very seldom are things actually free.
It has been a while since I've ordered from CSUSA but I have been very pleased with their shipping/customer service.