Sales taxes and mail order
Even when sales taxes are charged on mail order items, you still tend to save on the fact that the mail order company has less in 'brick and mortar' expenses embedded in the price. However, sales taxes in the US are much more complicated than what I recall VAT taxes being, from my time in Germany. Not only do the categories of items that sales taxes apply to vary from state to state, but you also have sales taxes applied by counties, cities, and other layers of government. Those borders don't always correspond with zip codes, so the task of determining what sales taxes to collect, which is relatively simple to perform for a local retailer, is extremely difficult for a mail order retailer to perform accurately.