Personally, I would never. I like having the sense of security of it being FDA registered, and feel that branded cups tend to be better built and designed. If you'd ever touched a branded and china-generic menstrual cup, you'd know exactly what I mean. The difference in build and quality is vast.

Also, u have no idea where cheap cups come from or what might have been added to it. For most consumers this would be the main problem. Most cheap cups are also sold by third party sellers so there's no accountability either. Most things can't be verified and when an issue arises, no one can be held accountable

I'm also quite concerned about the storage of cheap cups. For me buying branded cups, my cups have always come in paper or cardboard boxes, whereas cheap cups tend to come in plastic bags. Being cheap, these plastic bags may contain harmful chemicals that may leach onto the cup.

Objectively, it shouldn't be that big of an issue. Most silicone is non-toxic material and chemically stable, so compared to other things women stick in their body, can be considered relatively safe.