A new study from the Urban Institute finds lower income Americans paying 10-20 percent of their income on ObamaCare health benefits. These high costs come after generous federal subsidies covering premiums for individuals making up to $55,000 a year are considered.

Of course, the least healthy are paying even more of their income for ObamaCare, providing an overdue lesson on how insurance works.

While the ObamaCare law caps the premium costs of those receiving federal subsidies, beneficiaries can still face high costs due to co-pays and deductibles. In one example from the study, a group with the lowest income faces out-of-pocket expenses more than double their capped premium payments. For this group of Americans, ObamaCare costs almost 20 percent of their total income.

According to the Urban Institute study, almost one-in-five American families still report difficulties paying medical bills. This is down only slightly from before ObamaCare took effect.

Most political debate over health care in the nation concerns obtaining health insurance coverage. The centerpiece of the ObamaCare law is a complicated mechanism to mandate health insurance coverage, dictate the parameters of that coverage and subsidize the costs of the coverages’ premiums.

Health insurance isn’t just a benefit, however. It is also, at its most basic level, a cost-sharing arrangement. Even with the most generous health insurance plan, an individual is responsible for at least some portion of health care costs. These are paid through “co-pays,” where an individual pays a set percentage of any procedure and deductibles, where individuals pay most medical costs up to a certain threshold, after which health insurance begins paying.

Premiums increase or decrease based on how high of a “co-pay” or how high of a deductible an individual is willing to absorb. A “catastrophic” plan insuring against major medical emergencies, for example, could have a fairly inexpensive premium with a $10,000 deductible. The premium is low, however, because the individual is generally responsible for the first $10k of medical expenses, after which the insurance covers the bills.

ObamaCare’s main focus is on the first part of this equation; helping people obtain health insurance coverage by regulating the costs of premiums. Using this health insurance coverage, however, triggers new costs that have been only lightly addressed by the political dialogue. In fact, the political rhetoric, by focusing exclusively on access to health insurance, has left the public totally uniformed about how insurance actually works.

The Urban Institute study notes:

The combination of high premium contributions relative to income and high out-of-pocket costs for those with significant health care needs leads to individuals at those income levels paying 16.7 percent to 22.8 percent of income for their medical care. Thus, even with all of the ACA’s financial protections, individuals across the income distribution who are ineligible for Medicaid can still face very high expenditures.

The Urban Institute study would normally be an interesting, albeit dry, topic of discussion in a class on health economics or the limits of tackling huge challenges through public policy. The findings, though, should signal a serious warning alarm for the future of ObamaCare.

The fundamental vulnerability of ObamaCare is that relatively healthy individuals would decide that the costs of even subsidized coverage exceeded its benefits. According to the Urban Institute study, even relatively healthy individuals are paying over 15 percent of their income for ObamaCare health insurance plans.

The costs for insuring those with even modest health care needs are in effect subsidized by these healthier individuals. If these healthier Americans decide that even the subsidized costs are too high, they will likely opt out of the program entirely. This will push the costs of those with more health care needs even higher, creating what economists warn could be a “death spiral,” where both premium and out-of-pocket costs skyrocket.

These rising costs push even more people out of the program.

It cannot be overstated that the higher costs identified in the Urban Institute study have arisen in the first two years of ObamaCare, when overall costs were expected to be more restrained. Insurance companies charged relatively low premium costs, on the assumption that the pool of those covered would increase dramatically, offsetting the costs of the less healthy.

The health insurance industry, given a leading role in drafting the ObamaCare law by then-governing Democrats, were also promised offsetting payments from the federal government in the first few years of the new law to ensure premiums were affordable. While this was partly successful, it didn’t alleviate the shock most people experienced after they sought medical care through their new ObamaCare coverage plans.

ObamaCare has survived a number of constitutional challenges. The law has even survived two Republican landslide elections delivering control of Congress to opponents of the law. In the end, though, ObamaCare may be most vulnerable to itself. With costs rising higher than expected, the very premise of ObamaCare looks unsustainable.

It may be time to dispense with repeal and simply start over from scratch.