On some level, it’s a simple PR play. By offering a big, splashy reward they ensure that the next time a researcher is looking to cash in an exploit or a spyware company is looking to buy one, Zerodium will be one of the first names they think of. But it also reflects an increasing reality for anyone in the business of breaking into iPhones. It’s hard work, and getting harder. Speaking to Wired, Zerodium was quite explicit about why the price had increased, saying, "We’ve increased the price due to the increased security."

Of course, no security system is perfect. Apple can’t make it impossible to break into an iPhone, so the company has to settle for the next best thing: making it expensive.

We know it’s possible because we’ve seen remote jailbreak attacks before. In August, researchers discovered one developed by the spyware company NSOGroup, and deployed against an Emirati human rights activist. That was a rare find for researchers — and major news as a result — but it’s entirely plausible that a similar bug will turn up for iOS 10. If it does, the high price mostly ensures that anyone who knows about the bug will keep it secret for as long as they can.

There are a few forces driving up that price. The simplest one is Apple’s soon-to-be-launched bug bounty program, which hadn’t been announced when iOS 9 launched. The bounty program can’t compete with Zerodium on price for structural reasons. But it’s still offering $200,000 for the same bug — and any researchers who are worried about their work being used to target human rights activists might be happy to settle for the lower sum.

In a broader sense, the iPhone is also uniquely able to defend against this kind of attack. Apple manufactures the iPhone’s A-series processor, which lets it code private keys and other roots-of-trust directly into the hardware in ways that are impossible for software to read. That’s exactly the setup you want for defending against remote jailbreaks, and it’s unique among consumer devices. The typical comparison is Android phones (a similar jailbreak of Android 7 Nougat only gets $200,000 from Zerodium), but it’s equally true of Apple’s own MacBooks and even security-focused government hardware. That kind of integration between an operating system and chip-level hardware simply isn’t something you’ll find anywhere else.

But as the Zerodium bounty should remind us, that still doesn’t buy you perfect security. All it does is limit your attackers to those who can fund their own research groups or pay top-dollar to brokers like Zerodium. Almost always, that means governments — both good and bad. It’s one of the uncomfortable truths of the vulnerability market, and one of the reasons the "cyberwar" idea is so unsettling for civil rights groups. Even the best security can’t protect every phone against every attacker. All we can hope is that the price keeps getting higher.

iPhone 7 and 7 Plus review