All products can be faked, but I thing that GP means "cannot be faked without being obvious". Obvious fakes are not as much of a problem since Amazon has a pretty good return policy.

In the "cannot be faked" category, you can have:

- products so cheap that making a fake wouldn't make sense. for example an unbranded glass jar won't be faked because anything that looks like a glass jar but isn't a glass jar will be more expensive than a glass jar.

- products too complex and/or too low margin to be worth faking. For example, you will probably never find a fake desktop printer, as even the most simple printers are hard to make and sold at a low margin, maybe even at a loss. However, consumables are (very) high margin and you will find fakes, lots of them.

- products that have effective anti-counterfeiting systems. For example, Nintendo Switch games.