A "Benjamin" is the limit for many people when it comes to Obamacare.

Most Americans say they can't pay the monthly premiums that are routinely charged for Obamacare plans — unless they are eligible for federal financial assistance that lowers their price for that coverage.

That's the finding of a HealthPocket survey, which asked people what was the most they could afford to pay for coverage in 2017. Many Obamacare plans are significantly increasing their prices next year.

A total of 52.5 percent of the 1,133 people surveyed said they could afford a plan up to $100 per month.

Another 15.9 percent said they could afford $200. And 11.6 percent said they could handle $300, according to HealthPocket, an insurance comparison site.

Just 20 percent of respondents said they would be able to afford a plan that costs more than $300.

HealthPocket's head of data and research, Kev Coleman, noted that most Obamacare plans cost more than $300 per month, before subsidies are factored in.

The average price nationally in 2017 for a bronze plan — the cheapest Obamacare tier — is $311 per month for a 30-year-old nonsmoker who does not qualify for subsidies, Coleman said.

"That's up 21 percent from last year's average," he noted. Bronze plans cover about 60 percent of their customers' health costs.

And the average price nationally next year for the next tier — silver — will be almost $365 per month for a 30-year-old. That's a 17 percent increase over 2016's average.

Silver plans, which cover about 70 percent of their customers' health costs, are the most popular plans sold on Obamacare marketplaces.

Coleman said there are no bronze plans available nationally that cost less than $100 per month for a 30-year-old nonsmoker without a subsidy.

And just 1.4 percent of bronze plans nationally cost less than $200 per month for that same unsubsidized person, he said.

Another troublesome finding for Coleman was that millennials ages 18 to 34 were more apt than other groups to say $100 was the most they could afford.

More than 60 percent of millennials cited that limit.

"The millennial group is highly attractive to insurers because they are statistically more likely to use fewer health care services than older age groups, thus helping to control premiums within a risk pool," Coleman wrote in a report on the survey findings. If millennials steer clear of insurance, it could increase prices for others who do buy the plans.

Federal health officials have stressed that most people who buy coverage from a government-run insurance marketplace qualify for subsidies that significantly lower the premiums.

About 77 percent of the customers on HealthCare.gov, which serves 39 states, will be able to find plans that cost them less than $100 per month after subsidies, according to Sylvia Burwell, secretary of the U.S. Health and Human Services Department.

Subsidies are available to people whose household incomes are 100 to 400 percent of the federal poverty level, or $24,300 to $97,200 for a family of four.

Burwell on Friday tweeted a television ad running nationally since last week that says "because the majority of people who sign up qualify for financial help, most don't pay full price" and can find plans that will cost them $50 to $100.

But Coleman noted that not everyone qualifies for financial aid, or buys plans on the government-run exchanges, and therefore must pay full price for their individual health plans.

Coleman said that while subsidized customers "are highly motivated to enroll in coverage," those who don't get such aid may be less likely to sign up this year because of the double-digit percentage premium spikes that many plans are seeing.

Coleman said recent data suggest that higher premiums for 2017 could be slowing enrollment in Obamacare among new customers.

Earlier this week, the Health and Human Services Department said that more than 1 million people had selected a plan on HealthCare.gov during the first two weeks of open enrollment for 2017 coverage. The tally represented a slight uptick in the number of customers who had selected a plan in the first two weeks of 2016 open enrollment.

But Coleman noted that only about 24 percent of those sign-ups in the first two weeks of November came from new customers. Last year, 34 percent of the sign-ups in the first two weeks came from new customers.

Coleman called the drop in sign-ups "worrisome," pointing out that the Obama administration has been "trying to increase enrollment, obviously, to stabilize these risk pools so that premiums don't continue to spike."

If a risk pool, or group of customers of insurance plans, contains too many people with health problems, insurers have to raise premiums to offset the costs of providing them health benefits. Insurers this year have blamed their price hikes on risk pools that have been less healthy than expected.

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