A first edition has no value to me. The value comes from the words on the page, not the paper it’s printed on. I could see value in a book that was hand transcribed or something, but the fact that it was the first book out of a printing press is worthless.
I should say being signed is important, but that’s not really a rarity issue. That’s now a unique historical artifact because it was interacted with by a specific person. That’s basically the same as a bible having historical value because of who owned it.