At the moment it might be negligible but in the long run they are hurting them self. 5 years ago I and a lot of my friends ordered everything on Amazon because it was fast and we knew that we will get the correct stuff.
Nowadays I (and most of my friends) almost stopped using Amazon because it is such a hassle to find stuff which is actually sold and shipped by Amazon and not some sketchy third party seller with only 5 reviews. And even if you manage to order something directly through Amazon you might still have problems with counterfeit items and other stuff.
And the same is true for my parents and their friends. Until 1-2 years ago Amazon was _the_ place to shop online but nowadays they switched back to more traditional methods.
Due to all this shady stuff Amazon lost me as a customer (who used to spend hundreds and thousands of euros per year).
I trust Target's supply chain about 100x more than Amazon and I'm willing to pay extra for that assurance.
As a fairly heavy Amazon customer for both home & biz, I was getting to the point where Amazon was just the default buying location, but now there are entire categories of stuff that are such a PITA to find a valid offering that Amazon is just about off my list.
Amazon recently keeps showing me a popup about a Biz account for some benefits, and while I probably would have jumped at it 2 years ago, I just haven't bothered now.
Yes, it's mere anecdote, but I'm seeing many complaints of the same. This is the kind of problem that doesn't show up in the numbers early, and by the time it shows up in the numbers to get Mgt's attention, it may be too late, because the reputational damage has been done.
Years to build trust, minutes to break it...
Meanwhile, those counterfeits allow Amazon to fulfill orders more quickly and to list items at lower cost, undermining their competition, and any bad experience a customer has can be blamed on the vendor, not Amazon itself.
Of course, I could be wrong, and I have no particular insight, but to me this seems like an intentional part of Amazon's business model.