I think it's a cheap offer. If you are a professional well introduced in the business of selling 0days, for a gem like that, you can charge even a single customer of the same amount. Indeed there are private companies offering even more (https://www.securityweek.com/zerodium-offers-2-million-ios-h... )! Ok, companies involved in this business have some "safeguard" clauses in case the hole is discovered too soon (see for example the Hacking Team e-mails), but you can sell this kind of vulnerability practically to everyone. So the offer IMHO is a public relation move.