Silk isn’t cheap!

Back in the old days when prices of goods in stores reflected the real cost of making them (and not what the public would stomach), I wonder if things were different. I’m talking about the retail price of different sized clothes. Has it always been the case that a Small costs the same as an XXL even if it uses a third the fabric? They reduce the price for kids clothes, so why not different adult sizes? I guess it just became a non-discriminating convention and wholesalers factored their price around an average person, so they lost out on the big sizes and gained on the small.
It’s not something that occurred to me until this morning when I read about a UK bra manufacturer being targetted by a group of angry women who rallied on Facebook for charging more for larger sizes. I guess bra’s inflame the passions of both sexes.