Just because Amazon can ship stuff via a no-freight buy-in program and get it to you in two days (soon to be delivered by drones?), does not make that the market standard you should strive to achieve.
Amazon has spent billions of dollars to get where it is. The investments in technology and distribution power are off the charts. You have likely never spoken to someone at Amazon who knew anything about what you called about. Who even calls Amazon???
Here is what to do to be indifferent to Amazon and not feel trapped by the Amazon expectation:
The people buying at your website (or even your Amazon store) are buying from you because you are NOT Amazon. Don’t pretend you are. That only makes it worse. Make your responses thoughtful and human and be sure to give them all they might want if they were standing right in front of you making the special purchase they hunted down, because, that is exactly what they did. Your reputation is riding on it.