I've been chatting with this guy and he has been very communicative and seems legit so far. Agreed that the eBay protections may not be in full effect here, but I understand his rationale for listing the way he does. You can buy the seat in the listing as is for the price listed, or he'll custom reupholster it for extra. He has listed newly redone seats in the past too, near the price he's asking for custom.
He has a Facebook page where a few of his customers have commented:
https://www.facebook.com/Recaro-Max-134197476946402/
I may move forward with this, I'll keep posting with updates.