The item copy describes it as an "open jacket in grain de poudre wool," but wool makes up only 10% of the fabric composition (satin makes up the leftover 10%).
The design is based on Yves Saint Laurent's iconic smoking jacket, which was made of wool with a "grain de poudre" texture. (Saint Laurent Paris currently sells "Le Smoking" tuxedo trousers composed entirely from the iconic fabric; they cost $1,150.)
The sequin embroidery, done in the label's signature babycat print, appears elaborate; the construction process was presumably time-consuming and skill-intensive. But given the garment's cost, it's surprising that YSL used only a drop of the luxe wool listed in the product description, choosing to rely mostly on a synthetic fiber which has the reputation for being cheap and kind of tacky (not that trendy animal print blazers worth two years' tuition at a private college are a paragon of taste).
As fashionista-ta said in the Forum thread, "I can understand needing to cut costs on this piece, but what about non-virgin wool instead of polyester?? Even (perhaps especially) filthy rich people sweat."
The item is no longer available for sale on the website, and when I called YSL's personal shopper service, they said it wasn't in stock anywhere in Europe (I was not able to find a record of the garment ever having been sold in the US).
I reached out to the Saint Laurent press office asking for additional production details and some information about how the brand determined the price for this item, but have not heard back.