Riders by Lee, Low Super Skinny jeans for a fraction of the $89.99RRP. (For females I'd assume, though I'm not judging)
The sign claimed they came in sizes 4-13, but mostly smaller sizes, lots of size 7s, and I saw a 12. However they might run small because they have absolutely no stretch, and unfortunately you can't try them on (Although I saw a lady trying to squeeze into a pair in the middle of the store)
A link to what they look like:
http://www.shoptilyoudrop.com.au/eboutique/fashion/Riders-By…
They came in at least 3 variations that I could see (blue, blue-black, white or brown stitching) and there was a pretty big pile left.
Got a question where is exactly Costco? I tried their address on the web but it is not there either they put it wrong or my gps sucks