It probably is a better solution (I use one myself and my only gripe is that I wished I'd known it was an option as a teenager and not already been 30 when I discovered them), but if the menstrual taboo is as strong there as that article implies, then it may be an even harder sell than a man designing a napkin machine.

There's a lot more potential hand-contact with menstrual blood when using a cup than pads, and while someone in the western world might scoff at the idea that using a cup could "ruin" a women's virginity, that could be a real concern for an unmarried girl in rural India.

A great point about 'ruining virginity'. It is definitely a very sensitive topic in India and would severely affect product adoption.

From the linked Wiki page.

"Cup manufacturers urge the use of clean water for cleansing. This may not feasible in all countries or conditions, and alternative ways of managing menstrual flow will need to be employed"

They are great, but I can imagine they might be difficult to manage and to keep clean in some situations.

Not sure about the natural rubber ones, but the silicone ones can be boil-sterilized. But again, then you run into the taboo. If you can't afford sanitary napkins, can you afford a pot specifically for boiling your cup? Would you even be able to get past the taboo to boil it in the same kitchen that you prepare food in, even if it did have its own dedicated pan that never touched food?

Edit: Oh, and as jackityquack mentioned in the sibling comment to this one, that requires running water. I didn't even think it that far, but yeah...that's an even bigger barrier.

Like without running water.

And, yes it might be the most cost effective, but if you can't convince a white person to use it, then we shouldn't be telling Indians to use it either. It's an option, but the market should and will decide. (p.s. my roommate uses one too.)