Only places I've ever seen come close are Yoox (they typically have two or three Belvest suits and a bunch of Caruso, some of which will be in the $1k range). Not particularly familiar with the others.
My guess is that Yoox is offerering a "difussion line" Their clothes look nothing like my Belvest sutis/jackets.
Nor for that matter my Isaia, Sartoria Partenopea, etc.
Try these guys. They sell Belvest mostly size 40. Not the short tight trendy...