Refer to your original comment: "This is false. You do not get Amazon rates for shipping using SFP."
I took this mean that you do not get any discounted rate from Amazon for shipping using SFP. If you're now amending your claim to say that a SFP seller has access to "Buy Shipping" rates, then yes we agree. And if you're conceding that "Buy Shipping" rates are cheaper than those available to other businesses, then we agree again.
At no point did I claim that an individual merchant is getting the exact same quote to ship a package as Amazon would. UPS/FedEx wouldn't allow this, since pickup points are different, etc. But, it is certainly because of Amazon's volume that merchants who want to sell with a Prime badge can now get deeply discounted shipping rates. This is what I meant by "negotiated rates for UPS/FedEx/USPS that Amazon has access to".
> I'm not even the only one replying to you that disagrees with your claim
At the time of your comment, who else is disagreeing? This comment (https://news.ycombinator.com/item?id=18695969) is saying that Amazon's negotiated rates "aren't better". Better than what? Even you agree that buying through Amazon's "Buy Shipping" services are better than the baseline rate tables from UPS/FedEx. What I'm saying is that these rates are better than even the ones available to a merchant doing significant volume.