Today womens stockins and pantyhoses are real mass products and everywhere available for low cost. The industrial production of chemical fibers such as nylon or spandex is becoming more sophisticated and it can be produced faster growing.
An ordinary modern pantyhose with a thread strength of 15 or 20 DEN is very cheap, sometimes less than two Euro. And anyhow, some companies have been able to be produced exquisite and expensive stockings and pantyhoses in order to maintain on the market. For example the french premium manufacturer such as Gerbe or Cervin.
The old, original fully fashioned nylons are still very desired. Mainly from collectors of vintage lingerie, nostalgians and fetishists.
Company or producers of stockings which are owns an original flat-knitting machine (cotton-machine) knows what good inventory thy have in there hand. Also if the manufacturing by using this old mechanical machines will not be so fast such a modern knitting machine and quality control must be done by human eyes and hands.
By the way, the most women has stored a pair of fully fashioned or RHT stockings, or at least a pair of hold-ups in their stockings-drawer.