I have mostly stopped buying small electronics on Amazon, going to AliExpress instead. You get the same thing for much cheaper. The value Amazon has is in shipping time, but you pay a hefty premium for that.
It is important to note that the cheapest, unbranded (or counterfeit) products may actually miss components. Looking at the PCB, you may see an empty slot where a MOV or a filtering cap should be, underspecced components or blatant counterfeits (no, that cap is not a Nichicon!). They may be from the same factories, but brand names usually don't get that low, and they have people on site making sure the factories don't pull these stunts on their batch.
It is important to note that the cheapest, unbranded (or counterfeit) products may actually miss components. Looking at the PCB, you may see an empty slot where a MOV or a filtering cap should be, underspecced components or blatant counterfeits (no, that cap is not a Nichicon!). They may be from the same factories, but brand names usually don't get that low, and they have people on site making sure the factories don't pull these stunts on their batch.