Since its 2016 launch, the Snoo Smart Sleeper, a robotic bassinet, has captivated new parents—many of whom swear it has allowed for much more restful nights for both themselves and their babies. But at $1,700, the bassinet Babylist named the best smart crib has also been called the world’s “most polarizing baby product.” Now the recent introduction of a premium subscription model for some of the Snoo’s features has parents whining about the overall cost of the smart bassinet.

Happiest Baby, the company that sells the Snoo Sleeper, recently launched a premium monthly subscription of $20 per month for parents to access certain features for the smart bassinet. While many parents buy the Snoo outright from Happiest Baby, there is a massive online resale market for the smart sleepers, ranging from about $500 to $900—still two to three times the cost of your average bassinet. Given the Snoo’s eye-popping retail price, it’s no wonder that even the most desperate parents buy the device used rather than shell out most of a month’s rent—but now some believe their Snoo won’t work since Happiest Baby introduced the subscription model in July.

“It's a bit maddening. I understand [Happiest] Baby, parent company of Snoo, is a business and they need to make money,” Veronica Cutley, a mother of twins who bought two Snoos secondhand, told Fortune. “I understand that it must be frustrating to them to see new sale prospects go unrealized because they purchased used units, like I did. But…it saddens me greatly to see a subscription cost foisted upon new parents who are in a very vulnerable mental state—at their most desperate, helpless, exhausted life stage.”

Some say the Snoo is the latest victim of the everything-as-a-subscription economic model, where customers are increasingly pushed to pay monthly fees to access items (music, software, car features) rather than owning them outright. “This is also new territory when you consider that usually subscriptions start from the get-go of a purchase, but are not levied against a used item,” Cutley said. “That is unique. And I bet folks are thinking that's petty and ridiculous. It's just not done.”

But what many parents who have bought the Snoo secondhand don’t realize, according to its maker, is that their device will still work—regardless of a subscription purchase.

“You don’t need a premium subscription to get the key benefits—including the ‘smart’ benefits—of Snoo,” Lexi Montee Busch, Happiest Baby's vice president of marketing and communications, told Fortune in a statement. “The bed has full functionality, safety features, and automatically responds to your baby’s needs without using Wi-Fi or the app at all.” She also noted that anyone who bought a Snoo from Happiest Baby or an authorized retail partner before July 15 will still have access to all premium features.

The $20 premium subscription includes extra features such as sleepytime sounds (which play only at bedtime before a baby is put in the bassinet) and car-ride mode, which simulates the sounds and motions of a car ride.

“Parents who purchase or rent Snoo from Happiest Baby or an authorized partner will get free access to a premium app subscription. Those who borrow Snoo from a friend or family member or purchase Snoo secondhand can use the free app—which has everything needed for day-to-day use of Snoo like motion limiter, sound controls, and more—or they can choose to upgrade to a premium subscription,” Busch said. She added that parents also have the option of renting a Snoo for $159 a month to get all the subscription features.

Parents have turned to online forums, however, stressed at the thought that their smart bassinet won’t work at all.

The frustration among parents can be likened to purchasing a used Peloton. When you buy the Peloton, the bike still “works” in the sense that the pedals still move and you can get a workout in. But purchasing a subscription to Peloton allows you to take workout classes. It’s the same thing with Snoo. If you buy a Snoo secondhand, plug it in, and put your baby in it, it’s still going to rock your baby to sleep and play soothing sounds. But the subscription model means parents who bought a used Snoo will need to pay to access more advanced features like sleep, feeding, and diaper tracking, or adjusting the responsiveness of the bassinet’s rocking.

What the Snoo Sleeper does—and why it’s so expensive

The Snoo Sleeper was invented by pediatrician Harvey Karp, who is also the author of a parenting favorite, The Happiest Baby on the Block. While the features of the Snoo Sleeper such as rocking your baby back to sleep and calming sounds undoubtedly make middle-of-the-night feedings and restlessness more comfortable for parents, the inspiration behind it was actually to lessen the rate of SIDS-related deaths. SIDS, or sudden infant death syndrome, can occur when a baby rolls onto its stomach during sleep, and 3,400 babies die each year from the condition, according to the Centers for Disease Control and Prevention.

Despite its cult following, the Snoo has its detractors.

“Some parents swear by motion and say it helps their baby sleep for longer stretches. For others, the motion didn’t seem to make a difference one way or another,” Karen Reardanz, a baby products and registry expert at Babylist, told Fortune. “There’s also the concern that some babies may become dependent on motion for sleep and will eventually have to be weaned from it in order to sleep independently.”

Happiest Baby calls the Snoo an “extra set of hands,” that responds to the baby’s fussing so parents often don’t even recognize their baby has woken up, allowing parents more sleep.

“It was worth every penny,” Cutley said. “It took forever to convince hubby to go for them [because] they are pricey, but he humored me. And even he now says they were worth every penny. Our newborns could sleep three to four hours at a time coming home from [the] hospital, [and a] few weeks later five to six hours. Then seven to eight hours soon enough. Maybe we just got lucky? But I say the long sleeps were thanks to Snoo.”

The Snoo Sleeper also connects to an app in which parents can track sleep and motion via a free or a premium model.

“The reason people are spending this much money is because there wasn't another bassinet that really did that,” Brittany Sheehan, a pediatric sleep consultant and founder of Brittany Sheehan Sleep, told Fortune. “People loved the idea of a bassinet that was going to help put your baby to sleep, so you wouldn't have to get up in the middle of the night.”

A typical bassinet retails for a couple hundred dollars, with a “nicer” non-smart bassinet retailing for $500 or more. There are few comparable products to the Snoo Sleeper. The 4Moms MamaRoo Sleep Bassinet retails for less than $500 on Amazon, and provides automated rocking and shushing like the Snoo, but parents have to manually turn those motions on and off.

“You can get a very nice bassinet that is designed with safe sleep in mind for around $200 to $300, but the Snoo has advanced electronics and has an app,” Jennifer Johnson-Latulippe, CEO of baby and kids products company Gladly Family, told Fortune. She noted that the Snoo has also received De Novo authorization from the FDA for its ability to keep sleeping babies on their backs, making it a medical device.

“We spent years working toward FDA De Novo authorization to help propel us towards HSA/FSA and insurance coverage so that Snoo can one day be covered like a breast pump,” Busch said, adding that Snoo partners with companies to provide parents with free Snoo rentals for up to six months as an employee benefit. “The introduction of a subscription model was a necessary step to be able to continue working toward making Snoo even more accessible, and to allow us to continue to provide all families valuable support.”

The secondhand Snoo market

With the Snoo, as with most other baby products, parents seek out more affordable options from friends, family, and online marketplaces. And there’s a pretty robust secondhand market for Snoo Sleepers online, with prices varying greatly based on location, use, and other factors.

For example, Cutley, the mother of twins, purchased two used Snoos and sold them after her twins outgrew them. The bassinets’ resale value is anywhere between $500 to $1,000, she said, with some coming with accessories including sleep sacks, swaddle blankets, risers, and sheets.

“I think it’s worth the used price,” Cutley said. “Maybe if the company sold them at the used price, they wouldn't be fighting this black-market surge of used Snoos that they have to chase down and charge subscriptions for.”

Still, it’s likely Snoo will remain a popular purchase for new parents who can afford it. "People will pay anything for better sleep,” Babylist founder and CEO Natalie Gordon told Fortune. “And even when there is negative press about the Snoo, people always name how much they love it and how much it helps their family."

This story was originally featured on Fortune.com