Few New York start-ups have garnered the attention of investors and consumers in recent years the way ClassPass has. Its co-founder and C.E.O., Payal Kadakia, is a world-class dancer whose first company, Classtivity, never caught on with investors. She pivoted the company, and it’s since taken off: ClassPass raised $84 million from investors and has spread to 30 cities. The fitness start-up, which lets users pay a flat monthly membership fee to sign up for unlimited classes at studios near them, is said to be valued at $400 million. Customers loved ClassPass because it was a steal of a deal; in the early days, users paid $99 a month for access to unlimited fitness classes. “I’ve used Classpass since the very beginning. I was a beta user, and had to get invited to join,” one user told me. “I was so excited because I could honestly work out in N.Y.C. without feeling like I’m trapped in one location, or breaking the bank.”

But then, last summer, ClassPass bumped up its prices to $125 per month in New York, its first market. Users weren’t happy with the 25 percent hike. Then, on Wednesday, the company sent its New York customers another e-mail: ClassPass has decided that the one-size-fits-all membership model wasn’t working, so they’re ditching it in favor of a tiered (and presumably more sustainable) system. Customers who want to continue paying the same $125 per month for fitness classes will be able to sign up for 10 classes a month. But if they want to keep their unlimited classes, they’ll have to pay $190 a month (new users will have to shell out $200 for the same). In other words, ClassPass is now more expensive than an upscale gym like Equinox. “We’re encouraged by the engagement on ClassPass and the tremendous growth we’ve had that shows we are fulfilling our mission of helping people live a more active life,” ClassPass C.E.O. Payal Kadakia said in an e-mailed statement. “But we have to evolve our business model and adjust prices in order to create long-term sustainability with both our members and the market.”

Predictably, users are not pleased. The unlimited plan that was sold to them for $99 a month just a year ago has since nearly doubled in price. “The price hikes last summer were fair, as more studios were being added, and overall the customer service was good,” a ClassPass user told me. “But this is insanity, and the fact they have literally doubled it since I’ve joined is bonkers. They should have done price hikes in tiny waves, not another massive one. I will continue to use the service until I find something else that works for me, but now that it’s spring in the city, it’s not even worth it.” The subscription business model that ClassPass uses has been tried by other start-ups too; Vive, a start-up that was hailed as the “ClassPass for blowouts,” changed its model from a $99-per-month subscription for women who wanted to get their hair done to a tiered subscription model, to eliminating the subscriptions altogether, ultimately opting for à la carte pricing less than a year after it launched. But Vive realized the unsustainability and difficulty of subscription pricing right away and took swift action; ClassPass has hesitated, and now it has dedicated users whom it will have to convince to pay more for the same service for which they’re used to paying much less.

As recently as last year, ClassPass seemed to have perfected a unique business model: it collected and purchased discounted inventory from a number of studios—whose fitness classes would otherwise have empty seats—and sold it to its users (that low, low $99-per-month fee). “Subscription business models appear very attractive on the surface—committed customers, recurring revenue, top-line velocity, high lifetime values—why not?” General Catalyst partner Adam Valkin, who led ClassPass’s latest $40 million round of financing, told Business Insider last year. “But in reality, building a subscription commerce model for a two-sided marketplace is challenging. Churn can spoil the party, on either the supply or the demand side. Those that get it right may find a large prize, but I believe there are high barriers to success.”