Most items are taxed multiple times. Every part supplier pays tax, then tax is paid again on the next higher level assembly sold, and again by the wholesaler, and again by the retailer, and so on. It's really no different when you sell something used. Companies may not pay sales tax but they pay income taxes that are just another expense built into the cost of the item.

I understand that companies don't pay sales tax on parts that go into something down steam, and tried to indicate that by saying they don't pay sales tax, but they do pay income taxes that are built into the product price. By the time a consumer buys a product it has a huge amount of taxes built into the purchase price. Personally, I think it would be better if companies did not pay taxes, and all taxes were paid at the point of consumption. People would have a much better appreciation of the total taxes that they are actually paying.