You might like to hear about Henrietta Lacks, arguably the first immortal human being, now called HeLa. Her living cells are one of the most widely distributed living human tissue available, still alive, still replicating because they have activated telomerase, which means the cells are not 'aging' in the way normal human cells do. I think it's about $400 for about a vial's size of tissue.

I do notice that only the mucus membrane, blood, hair, sweat gland, and hair follicle slides specifically say they're from a human, the others could be from a pig or any other large mammal and it would be very hard to tell the difference. Were I buying an assortment of electronics and a few items were labeled with a brand name and others were unlabeled, I'd assume the unlabeled ones were generic.

Also, one cadaver can generate an awful lot of slides. Each slide requires on the order of a microliter (1/1000 of a milliliter) of material, and a good microtome can cut samples with a thickness of a few micrometers (1/1000 millimeters). Essentially all medical students go through an anatomy class involving the dissection of a cadaver, and Google says there are 3.8 million doctors in China, so even with a generous assumption of 20 students per cadaver and a static field (it's not) with 50-year careers, that's still several thousand cadavers per year.

The Chinese, in particular, have access to human organs and body parts at rates that are much higher than even opt-out organ donation countries (where organ donation after death is nearly 100% due to the opt-out nature of their system).

This strongly suggests that “organ donation” in China is as-needed and on-demand from political prisoners and ethnic/cultural undesirables.