Icons for a variety of apps are seen on an Apple iPhone 6 inside the Apple store on 5th Avenue in the Manhattan borough of New York City. File picture: Mike Segar

New York - “The sight of lovers feedeth those in love,” William Shakespeare argued in a 16th century love story. Never have those sights been more common than 417 years later, when visions of potential adoration can be swiped at breakneck speed on any smartphone.

Between the countless mobile dating services on the market - Bumble, Tinder, Grindr, Her, OkCupid, Scruff, and Hinge among them - today’s young lovers have access to more potential mates than ever. And they're increasingly willing to pay for it.

Sights, meet wallet.

Among millennials' favourites are swipe pioneer Tinder, Sadie Hawkins-inspired Bumble, and Hinge, which boasts the most millennial-dominated user base. (Ninety percent of its users are aged 23 to 36.) These apps have gently begun to sway their user base to a paid model.

Tinder launched a paid monthly subscription - $4.58 to $9.99 a month, based on the length of subscription - and in-app purchases in spring 2015. Bumble was free until August, when it launched a monthly subscription service - $6 to $9.99 a month. The most recent convert is Hinge, which had been free since 2013 but this month began charging $7 a month for its paid service.

With the exception of Tinder, these apps don't sell advertisements. Their path to monetisation lies in persuading millennials who haven't before felt compelled to pay for dating that it will be worth it.

Scruff, a dating app for gay men, has already managed to do so. In 2011, it launched a paid version costing $9.99 to $14.99 a month. Today, a third of its paid subscriptions are bought by millennials, said Jason Marchant, chief product officer. From 15 percent to 20 percent of its more than 10 million users pay for the app.

Indeed, despite being debt-ridden and underemployed, millennials aren't necessarily averse to paying for dating. Among 18- to 34-year-old users of online bank Simple, the average monthly spending on dating services is $11.65.

But there's a tipping point for what they're willing to shell out: no more than $15 a month, according to an informal survey of about a dozen millennials. And when they pony up for monthly subscriptions, they want features unlike those offered in the apps' free versions.

For years, paid matchmaking services were the norm; some, such as eHarmony and Match, had steep fees, while others like OkCupid offered free versions but kept premium offerings for paid users. But starting with Grindr in 2009, free dating apps began attracting hordes of smartphone-obsessed millennials. Now the apps hope to keep them as they trickle out paid upgrades that promise to drive not just matches but relationships.

Tinder has said its own efforts to monetise have so far been simple, and successful. In the second quarter of this year, its parent company Match Group - also home to Match, OkCupid, and Plenty of Fish - saw revenue jump 21 percent from the prior year quarter, thanks to a 30 percent increase in its average paid-member count, led by Tinder.

“I've never really seen the monetisation of business go as smoothly as this has from sort of a standing start,” Chief Executive Officer Gregory Blatt said on a July earnings call.

That may be partly because apps such as Tinder come in just under the wire of what millennials consider an acceptable cost. Their monthly fees are roughly the cost of a month of Netflix or Spotify - or even the price of one drink on one of the many dates users hope to get.

That's how many rationalise the spend and determine the ceiling for what they're willing to pay.

“I think under $10 [a month] is perfect,” explained Dublin-based Thomas Crosse, 28, who has used Tinder for two years and has an annual subscription. “If it goes over $10, then they're trying to scam you, or it's just not worth it. But $10 - that's the price of a drink a month. You probably won't notice it. I forgot about it until it came up on my Google Play.”

Hinge, for its part, conducted market research to determine what monthly price would sit best with its millennial user base before setting it at $7 - part of its plan to cater to millennials more interested in relationships than in hook-ups. (Seventy percent of its users say they're looking for something serious.) After a three-month trial period for existing users, Hinge will be available only to paying users.

“Our testing showed us that $7 is around the right range that both indicated 'I'm serious, and I'm looking for something serious' but not 'I'm going to pay $50 on eHarmony’,” explained Karen Fein, Hinge's vice-president of marketing.

A monthly fee cheap enough that users can forget they're even paying seems key for luring millennials. Asked if she pays for OkCupid, Jennifer Johnson-Blalock, a 32-year-old New Yorker, couldn't remember off-hand, then signed onto her account to check.

“I still have this signed up,” she laughed. “Not to sound spoiled, but $30 every six months is small enough that it doesn't jump out on my credit-card statement.”

Johnson-Blalock now spends $5 a month on OkCupid; once, while in law school and trying to meet someone who wasn't, she spent around $10 a month on Match. She also uses the services of a matchmaker, which come at a much higher price that she declined to specify.

“I'm not opposed to the idea of paying for dating services, but it has to offer something of value,” she explained. “For me, it's really more about quality than price.”

She also uses Bumble, though she forgoes its paid option - not because of the price, but because she wasn't wowed by its features. She also has Hinge and she's interested to see how its foray into a subscription model goes.

One dating-app feature that got considerable praise from millennials interviewed was Tinder's “Super Like”, which lets users tell potential matches that they particularly like them. The app offers users one free Super Like every 12 hours, then upgrades them to five a day when they pay for the app. Tinder Plus subscribers can buy à la carte Super Likes at $4.99 for five, or $19.99 for 25.

“If you can get a date which could possibly be the person you'll stay with all your life, it's not that much money,” reasoned Crosse. “I thought, if you really fancy someone, let them know! Don't sit down and wait. So I paid for the Super Likes.”

After joining Grindr in 2011, Matt - who asked not to be identified by his full name for professional reasons - briefly paid for the app, whose users are two-thirds millennials. But he stopped, because he wasn't using the paid version's extra features.

“I don't really have a type,” the 29-year-old explained. “And if you pay for the extra version, you can filter more by age and tribes - like bears or something.”

He didn't feel he needed to pay for Tinder, either, because there were so many nearby users he was interested in on the free version. But like Johnson-Blalock, he said the price wasn't what turned him off.

He had happily paid, after all, for an app that doesn't do anything other than scramble his voice to sound like a guinea pig.