If you are not buying from Amazon, then nothing on the entire page should imply that you are.

Why is this not obvious to us? It wasn't to me either. There has got to be some cognitive bias at play here to lead to our acceptance of inverted principles like this. The framing of the problem is completely inverted, yet we're pretty much okay with that.

If it's not clear what I'm talking about here's another example:

"Why do you need privacy if you have nothing to hide?"

This is also a reframing that presumes I do not have privacy and therefore bare the burden to prove I need it. People accept this frame and attempt to argue it directly all the time, when they should really just say "Why do you need to take it?" The burden of proof is on the taker.

Neither the buyer nor the seller should be so accepting of Amazon's attempt to obfuscate the actual parties involved in the sale. Amazon is just the payment processor and possibly providing storage and shipping services.

A real world analogy would be if every store that accepts VISA looked like a VISA store.

I'd wager that a lot of people don't know what that means, as opposed to:

You are buying this from X. Amazon is only processing the payment.

And there's probably a way to word that even more clearly...