Independence Blue Cross' cheapest midlevel, or "silver," plan for a 25-year-old nonsmoker costs $201 a month. Aetna's is $273 a month, or 36 percent more. Both prices are before a tax credit.
An estimated 80 percent of people who buy health insurance on the exchanges mandated by the Affordable Care Act will be eligible for a tax-credit subsidy.
A 25-year-old making $25,000 a year would be expected to pay $144 per month for health insurance and would receive a tax credit for the rest, according to a subsidy calculator on the Kaiser Family Foundation website.
Michener said the gap between Aetna's prices and IBC's in Philadelphia and the surrounding Pennsylvania counties could stem from IBC's use of a "narrow network" for certain plans. Aetna is not offering such plans.
IBC is marketing them as HMO Proactive to attract customers willing to significantly limit their choices of hospitals and doctors in exchange for lower prices.
IBC said another factor is also in play.
"We priced our products this year at zero percent margin," which means the company expects no profit on the plans, Brian Lobley, IBC's senior vice president of marketing and consumer business, said Tuesday.
"We're really trying to make sure there's an offering for everyone," Lobley said during a break from an outreach session at the Rising Sun Health Center in the Olney section of Philadelphia.
Most of IBC's insurance businesses are for-profit, but IBC's holding company is a not-for-profit entity.
Insurance experts said there's a great deal of risk for insurance companies in figuring out how much to charge for insurance on the new exchanges.
"You price it up front, but you really don't know who's going to enroll," said R.B. Drennan, chairman of the risk, insurance, and health care management department at Temple University's Fox School of Business.
"We won't know for a couple of years what the loss experience is going to be," Drennan said.
Given that uncertainty, Aetna, which operates nationwide and insures 22 million people, decided to "enter the public exchange market gradually, with time to assess our strategy and evolve as we gain experience," Michener said.
The company is participating in exchanges in only 10 states, recently pulling itself off the exchange in New Jersey.
That left Horizon Blue Cross Blue Shield of New Jersey, the state's largest health insurer; AmeriHealth New Jersey; and Health Republic Insurance of New Jersey on the New Jersey exchange.
New Jersey rates are higher than those in Southeastern Pennsylvania because New Jersey has different rules about what must be covered by insurers, among other factors.
AmeriHealth New Jersey's cheapest plan for a 25-year-old costs $220 a month, compared with $187 a month for the cheapest plan being offered by AmeriHealth's parent, IBC, in Pennsylvania.