End-to-end encrypted messaging app Signal has long been free to consumers, but it's not cheap to keep the service up and running.

On Thursday, the nonprofit behind Signal revealed it’ll cost an estimated $50 million per year to run the encrypted chat app by 2025, due to the infrastructure and staffing costs. "And this is very lean compared to other popular messaging apps that don’t respect your privacy," it said.

The Signal Foundation disclosed the figure both to underscore the importance of donations to fund the messaging app, and to illustrate why the tech industry is always on the lookout for ways to monetize people’s private data under the guise of “free” apps.

“To put it another way, the social costs of normalized privacy invasion are staggeringly high, and maintaining and caring for alternative technology has never been more important,” the foundation says.

In a blog post, the foundation estimates it’s paying $14 million in infrastructure costs per year to run Signal. Over $4 million will go to server and storage costs while a surprising $6 million is necessary to fund the SMS-based registration codes sent to Signal users' smartphones when they sign up for the first time. These SMS service providers, usually mobile carriers, have been increasing their rates, which have led to the ballooning costs.

The nonprofit is also spending an estimated $19 million per year to pay for 50 full-time employees, who are maintaining and developing new features for Signal, which runs on Android, iOS, and desktop. “Our goal is to compensate our staff at as close to industry wages as possible within the boundaries of a nonprofit organization,” the group adds.

The Signal Foundation adopted a nonprofit status precisely to ward off any attempts to extract money from people’s private data. “To put it bluntly, as a nonprofit we don’t have investors or profit-minded board members knocking during hard times, urging us to ‘sacrifice a little privacy’ in the name of hitting growth and monetary targets,” the group says.

The end-to-end encrypted nature of Signal also prevents the foundation from collecting users' messages. The nonprofit’s storage costs merely fund the ferrying of encrypted messages, which are later purged from its servers. “We can’t read or access any end-to-end encrypted messages because the keys that are required to decrypt them are in your hands, not ours,” it adds.

Still, the growing costs naturally make us wonder and worry if Signal can continue to pay its bills as user numbers climb, resulting in higher infrastructure costs. For now, the nonprofit plans on relying on donations from a small group of well-funded donors, along with “a large number of modest contributions from people who care about Signal.” (In 2018, WhatsApp co-founder Brian Acton invested $50 million into the app. He’s since become a Signal board member.)

“We believe this is the safest form of funding in terms of sustainability: ensuring that we remain accountable to the people who use Signal, avoiding any single point of funding failure, and rejecting the widespread practice of monetizing surveillance,” the nonprofit says.