I found that NM/Barneys NY/etc carry cashmere (e.g. Brioni), merino, cotton (e.g. Zegna) that are quite thick. Â High quality thick cashmere and merino are not hot in summer. Â Boot socks tend to be thick but usually have too much heat holding synthetic Â fiber--same with running/hiking/etc socks at REI. Â And they are often rather ugly. Â Maybe Padagonia/etc has some nice thick socks.
I've never found any of Patagonia's socks to be dressy, though they're certainly thick. Press has some thick(er) wool socks.