While this should represent a long-term concern for Amazon but it is not a short-term one. For now they are benefited by potential buyers viewing their products as superior.
Incidentally, Amazon's real failure for me as a consumer is their delivery service. In spite of spending hours on the phone with their logistics departments, Amazon's delivery people have a roughly 33% success rate getting a package to my door, compared to nearly 100% for USPS, UPS and Fedex. This has diverted thousands of dollars in the last year alone to other vendors or in-person stores, as i preemptively avoid the frustration associated with waiting for a package that never comes and then having to chase down a refund or another shipment.