These are just a fraction of the medical expenses victims of the Boston Marathon bombing will face.

The mammoth price tag is probably not what patients are focusing on as they begin the long healing process. But friends and strangers are already setting up fundraisers and online crowd-funding sites, and a huge Boston city fund has already collected more than $23 million in individual and corporate donations.

No one knows yet if those donations — plus health insurance, hospital charity funds and other sources — will be enough to cover the bills. Few will even hazard a guess as to what the total medical bill will be for a tragedy that killed three people and wounded more than 270. At least 15 people lost limbs, and other wounds include head injuries and tissue torn apart by shrapnel.

Health insurance, as practically anyone who has ever gotten hurt or sick knows, does not always cover all costs. In the case of artificial limbs, for example, some insurance companies pay for a basic model but not a computerized one with sophisticated, lifelike joints.

Rose Bissonnette, founder of the New England Amputee Association, said that the moment she heard about the bombings, she knew immediately that her organization’s services would be needed. The advocacy group helps amputees navigate things such as insurance coverage for artificial limbs.

Bissonnette shared one group member’s struggle to get coverage for artificial arms as an example of the red tape some bombing victims could face. The woman “got a call from the insurance company and the person on the other end said, ‘How long are you going to need the prosthetic hands?'” Bissonnette recalled.

Bissonnette herself was in a horrific car crash 16 years ago that left her with injuries similar to those facing the Boston victims. Her mangled lower left leg had to be amputated and her right ankle was partially severed. Her five-month hospital stay cost more than $250,000. Health insurance covered all her treatment, rehab and her prosthesis.

Health economist Ted Miller noted that treating just one traumatic brain injury can cost millions of dollars, and at least one survivor has that kind of injury. He also pointed out that the medical costs will include treating anxiety and post-traumatic stress — “an issue for a whole lot more people than just people who suffered physical injuries,” he said.

Adding to the tragedy’s toll will be lost wages for those unable to work, including two Massachusetts brothers who each lost a leg, Miller said. They had been roofers but may have to find a new line of work.

Many survivors will also need help with expenses beyond immediate health care, including things like modifying cars for those who lost limbs or remodeling homes to accommodate wheelchairs.

Many survivors live in Massachusetts, a state that requires residents to have health insurance, “which should cover most of their required treatment,” said Amie Breton, spokeswoman for Massachusetts’ consumer affairs office. “The total cost of that treatment is impossible to calculate at this early stage.”

Amputees may face the steepest costs, and artificial legs are the costliest. They range from about $7,200 for a basic below-the-knee model to as much as $90,000 for a high-tech microprocessor-controlled full leg, said Dr. Terrence Sheehan, chief medical officer for Adventist Rehabilitation Hospital in Rockville, Md., and medical director of the Amputee Coalition, a national advocacy group.

Legs need to be replaced every few years, or more often for very active users or those who gain or lose weight. Limb sockets need to be replaced even more often and also cost thousands of dollars each, Sheehan said.

Massachusetts is among about 20 states that require health insurers to pay for prosthetic limbs, but many plans don’t cover 100 percent of those costs, Sheehan said. “Most are skimpy beyond basic prosthetics and they have not caught up with current available technology,” he said.

“The insurer will use terminology such as ‘not medically necessary'” to deny computerized feet or knees that can often make the patient better able to function and more comfortable and safe, Sheehan said.

Some insurers may be willing to make exceptions for the Boston blast survivors.

“We will work to ensure that financial issues/hardship will not pose a barrier to the care that affected members’ need,” said Sharon Torgerson, spokeswoman for Blue Cross and Blue Shield of Massachusetts, one of the state’s largest health insurers.

Harvard Pilgrim Health Care, another big insurer, is changing its policy and will pay for some of the more expensive bionic limbs when there is a demonstrated need, said Dr. Michael Sherman, chief medical officer. He said that 15 blast survivors admitted to hospitals are Harvard Pilgrim customers and that the insurance company is discussing “whether we might absorb some of the copays and deductibles.”

“This is a terrorist act, and our only thought here is about providing support,” he said.

The 26 hospitals that have treated bombing victims have charity funds that will cover some of the costs, said Tim Gens, executive vice president of the Massachusetts Hospital Association. Some injured residents may be eligible for Massachusetts’ public health funds for the uninsured or underinsured. People with huge medical bills they can’t afford are eligible, regardless of income.

Gens said hospitals are still focused on treating survivors, not on costs.

“It’s an extraordinary shock to so many individuals. The hospitals are working very hard to make sure that each family gets the support they need. Billing is not an issue they’re addressing right now,” Gens said.

At Massachusetts General Hospital, where 31 victims have gotten treatment, chief financial officer Sally Mason Boemer said bills “create a lot of stress. Our assumption is there will be sources we can tap through fundraising.” Boemer added: “Now is not the time to add additional stress to patients.”

A big chunk of charity money for survivors will come from One Fund Boston, established by Boston’s mayor and Massachusetts Gov. Deval Patrick.

The fund has gotten more than $20 million in donations. Determining who gets what is still being worked out, but victims’ insurance status and place of residence won’t be a factor, said Kenneth Feinberg, the fund administrator. He oversaw the 9/11 compensation fund during its first three years, distributing more than $7 billion to 5,300 families and victims.

Grass-roots fundraising efforts include online funds set up by friends and relatives of the victims.

Those victims include Roseann Sdoia, a Boston woman who was near the marathon finish line when the blasts occurred. Sdoia was hit by shrapnel, fire and a tree that became a projectile and injured her left leg, the funding site says. Her right leg had to be amputated above the knee. After several operations, Sdoia has started rehab.

“She is a fighter and her attitude is phenomenal,” said her friend and former sorority sister, Christine Hart, who set up the site. More than $270,000 has been raised for Sdoia so far, money that may help pay for an artificial leg, transportation to and from rehab, and modifications to her car or home, Hart said.

The donations will help make sure “that finances are not part of the burden” she has to bear, Hart said.

Other funds have been set up in communities like Stoneham, a Boston suburb that counts at least five current or former residents among the victims. A Stoneham Strong fundraising event is set for Friday evening, with participants asked to circle the high school track to show support for the marathon victims. Hundreds are expected, said organizer Shelly MacNeill.

“The outpouring has been unbelievable,” she said.

AP Medical Writer Carla K. Johnson contributed to this report.