Amazon is a platform for businesses of all sizes to sell their products and gain exposure (think eBay). Amazon isn't a direct rival of Companies A, B, or C but instead a helpful partner. Example: Walmart has a store set up on Amazon.
And sure, Amazon now has it's own brand and products that create more competition in the marketplace, but many of the products sold on Amazon.com are listed by individuals and small businesses as an exercise in retail arbitrage.
At the end of the day, if ANY company in the US can reduce its shipping cost they're going to. And Amazon is positioned to be a more valuable partner to many of these companies than UPS is anymore.
Sorry UPS, you're running a high risk of pricing yourself out of an industry that no longer needs to rely on a unionized work force in order to synchronize the world of commerce.
We're *.