Knitted tampons?

I'm thinking of developing a line of knitted washable tampons. The design would be something like this (only knitted instead of crochet). They would be machine washable.
I would sell them in sets of 6 probably, for around $20... (that would vary by the materials cost).
I am considering cotton, hemp, and bamboo. All are natural and absorbent fibers, and are washable. Any could be obtained in organic form, as well as dyed or undyed. My question is which fibers my potential customers might prefer...

• cotton is definitely the cheapest
• hemp is naturally anti-microbial, and is eco-friendly (whether organic or not), it is very sturdy, and starts out soft but some reports say it gets rougher with time and washing
• bamboo is amazingly soft, eco-friendly, but so far as I know it isn't as hearty as cotton or hemp

• organic fibers of course have fewer chemicals, and many people consider them safer, but they are expensive, and may be difficult to find certain blends
  
• regular (non-organic) fibers are much cheaper and easier to find
  

• undyed yarn has been handled less than dyed yarn of course, and has fewer chemicals in it
• dyed yarn (especially darker colors) would hide potential stains, as well as giving the option to have a rainbow of tampons, or of having one color for regular tampons and another for super