Large shippers generally do have access to similarly priced shipping options. It's difficult to directly compare because volume prices aren't all public.
Not sure where we're getting our wires crossed here....
You described the "if you or I wanted to send a three-quarter-pound package..." scenario as "very misleading", because "They aren't comparing apples to apples. In particular, they take a retail price for fast shipping with tracking and compare to a wholesale price for slow shipping without tracking."
I asked: "Do US sellers have access to this slow shipping option?"
You have not yet answered that question. The "you or I" in this context is not large shippers, and "similarly priced" is not the same as having access to the same shipping options (and prices) that individuals in China have.
No, US sellers can't ship using an international shipping program. It's two fundamentally different things.
You can try to set up a comparison that's closer. That would involve sorting discounts on the US side.
Chinese shippers sending packages through UPU are going through UPU wholesale rates, because they're all processed in bulk before it gets to the US. USPS doesn't pay for getting it from someone's local post office into the US, they pay only once it's already in the US. You can't compare that to retail prices someone pays at a US post office, because that pays for "first-mile" processing.
Comparing the cheapest international shipping program with one of the more expensive domestic options, when there are several differences I pointed out above, is misleading. You've yet to make a case that they're comparable.
