As to accessory webcams - there is definitely a market for high end webcams. The Logitech 920s or c or whatever was very highly rated and one of the first to disappear from shelves last spring along with their 4K model. I’m not saying it was objectively great equipment, just using it to illustrate that a webcam with high ratings will sell for a premium no problem. I don’t know about the margins for OEMs but I suspect there’s some room there when a $250 webcam is only marginally better than a $90 version.
I would easily pay $400-$700 for a “usb webcam” if it approached my iPhone camera’s quality and allowed me the control and capability of a cheap camcorder (think what a $250 Vixia comes with - manual white balance, optical zoom, adjustable frame rate, physical powered lens cover, IR remote control, tripod mountable, integrated confidence display - especially if you could leverage the USB connection to make the confidence display function as a teleprompter too). No question there’s a market for such a product. It would sell wildly in today’s market.