In trying to find out the answer to your question about the cost of muslin, I came across this picture. It really struck me to see it, and be reminded how fine a fabric muslin can be. When we use it today, it is as cheesecloth, because it is like a sieve for the whey.

What I want to know is would muslin just have been used like this as an overdress, and then a closer-weaved cotton such as calico been used for the underdress. Otherwise, surely dresses would have been a bit see-through?

And a muslin cloak? Not for warmth, surely?