Yep, I think this is exactly how things work. My household buys pretty much anything it can from Amazon unless it's more expensive than we can get elsewhere because our Amazon credit cards automatically give a 5% discount (cash back). Since we pay our balance every month this is basically like having 5% more income proportional to the amount spent on Amazon**

We never have a problem dealing with customer service. A simple chat solves pretty much everything immediately, and when it's Amazon's fault they'll apply a courtesy credit towards our account. (Actually that hasn't happened a lot lately-- maybe something they don't do as much any more, or maybe they've calculated that we're solid enough customers that we're not quiting Amazon just because Amazon didn't give us free money)

*The first time we used Amazon Fresh was a complete epiphany for us. I was sick so couldn't go food shopping. Instead I gave Fresh a shot, and found out that on average their prices were 10% to 15% lower than I paid at the supermarket, and* we still got the same 5% cash back from using our Amazon credit card. Even after a good tip for the driver, we were still saving money. In terms of selection, they probably lack about 10% of the things we normally buy or they're much more expensive (meats especially) so I still do the occasional trip to the local grocery store to stock up.