My only guess would be that are not far from the garment districts in NYC, couple years ago while in Philiadephia went to JoMar Textiles I purchased some fabric for my niece's prom dress and a few suiting fabrics, found out the prom dress fabric was just like a Vera Wang (It was hand beaded.) fabric, the suiting was like a fabrics used by Nicole Miller and Ralph Lauren.
The savings on these fabrics were unbelievable.
Just make sure you check if they are printed that they are on grain.

They probably sell mill ends. I'm Not quite sure what the term means but I think it is fabric that is left at mills when they change to a new design.

Just look on line there are many places that sell mill ends.

You are right I have bought mill ends and there is nothing wrong with them but sometimes there is. Just like outlet stores and seconds you have to watch what you buy, but you can get good bargains.