'Medicare for all' is a costly rallying cry.

• Position: YOUR LIFE

"When I signed in for my yearly mammogram, the receptionist announced with a wry smile, 'No co-pay this time; it's free.' We both knew that it's really not free," says Marilyn M. Singleton, a board-certified anesthesiologist who sits on the board of directors of the Association of American Physicians and Surgeons, Tucson, Ariz.

"To understand whether free means free, let's look at Medicare as an example. Medicare has four parts. Part A covers hospital admissions, post-hospitalization, short-term skilled nursing, and hospice. Part B covers outpatient medical services such as physician visits, lab tests, and outpatient surgery. Parts A and B are called traditional Medicare. Part C (Medicare Advantage) is private HMOs. Part D is prescription drug coverage. Technically, all parts are optional.

"Medicare is costly before and after we enroll. We pay for Part A through a 2.9% tax on earnings, half of which is paid by employers. Thus, an average worker earning $43,500 per year generates $105 every month for the promise of hospital insurance benefits beginning up to 45 years in the future.

"Importantly, Part A is mandatory for those eligible for Medicare who receive Social Security payments. If beneficiaries want to opt out of Part A, they must forfeit all of their Social Security payments."

Singleton explains that those ineligible for premium-free Part A because they did not pay the Medicare tax during their working years may purchase it (at a cost of $426/month in 2014) but, if they do not do so immediately, they are penalized. Their monthly premium can increase 10% and they must pay the higher premium for twice the number of years they could have had Part A, but did not enroll.

Just as with most private insurance, Medicare Part A has out-of-pocket expenses. The 2014 Medicare Part A inpatient hospital deductible is $1,216 per hospitalization and the co-pay for hospitalizations longer than 60 days is $304 per day. There is no out-of-pocket limit, Singleton points out.

"General tax revenues finance 72% of Part B; beneficiary premiums finance the remainder. The government deducts a minimum of $104.90 for Medicare Part B from the monthly Social Security payments of everyone enrolled in either Part B or Medicare Advantage. High-income earners--greater than $85,000 for individuals and $170,000 for couples yearly--pay progressively higher Part B premiums up to $335.70 per month. Part B has an annual deductible of $147 and co-pays of 20%, and a lifetime...