What is the proportion of edible meat in whole live mussels? The price of one kilo of mussels (blue mussels) here in my town is around 60–70 SEK (9–11 USD). I think that makes a large enough portion for two people, but when checking if all of them are alive and when cleaning them, the price runs higher. I'm interested in what the price per kilo of the edible part (the muscle) of the mussels are. In one mussel, how much by weight is shell and how much is muscle?
The Tourism PEI site says that one pound of mussels is 20-25 mussels, about one cup of meat, and that you can serve one person that for a main meal or two people for an appetizer. 

The Food and Agriculure Organization of the United Nations says:


  One bushel of whole mussels should yield from 6 to 9 pounds of cooked
  meats. Percentage yield by weight may range from about 8 per cent to
  as high as 20 per cent of the whole mussels.


Finally, this is 500g of mussels (my lunch in Brussels on a hot day - my companion has the same):


And this is how I can remember it was 500g: