The problem is not unknown value. It’s unknown cost. Until I know everything you will ever do to me with my email I don’t know the true cost. What I can guess—given the thousands of precedents I’ve encountered over the years—is that the total cost will be time taken from my short life to fend of yet more marketing and yet more marketers. For comparison, if you ask me for currency, I know the total cost of ownership. Usually, for me, a few units of currency are a rounding error compared to the value I place on time.

The total cost is how much time it takes to google "temp email" and then click on the first link and use that temp email to get the book. It should take about 2 minutes, maybe even less time than writing out your comment.

Sure, same as the total cost of a movie is how long it takes to type the name into a torrent search and click the magnet link. If the OP wanted a bunch of dead temp emails, why ask other people to input them. But, not my point.

I think on HN a good assumption is posters want to discuss, to get feedback. Also not a bad assumption the notion of temp email will be news to absolutely no one at all here.