It's a shame there aren't better pics/details of the $30 eBay cheapies.
The thing is, a snatch block is a very simple machine, really onl ya few ways you could vary teh manufacturing on it.
It's kind of hard to know how one might be "crappy" or not do it's job; it's just a pulley... besides maybe just thin metal that would tend to bend under stress? Or poorley specced bearing on the wheel? I assume there's bearing in there?
I'm just kind of thinking that this may be a case where more $$ may not get you a whole lot more.

With 200+ Billion electrical parts, the world most complicated machine is inside your own skull.

Question Reality.
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'89 Rnr DLX "SR4.5", 32s w/ 5.29 locked f/r blah blah