All AIDS conferences are about money. This one, more than most, was also about decisions. There are now far more ways to profitably spend money on AIDS prevention and treatment than in the past. And the benefits of spending more — which most countries are not eager to do — are bigger than ever.

Is it worth spending $7 billion more per year to speed the decline of new infections? Is there justification for providing HIV-prevention drugs to uninfected Americans when infected Africans are going without? Should pregnant women be put on treatment before men in order to prevent the heartbreak and expense of orphan children? Is being able to get a “viral load” test in an unelectrified village worth the cost of the hand-held device that makes it possible?

Those are just a few of the myriad decisions emerging from five days of conversation here at the 19th International AIDS conference that ended Friday.

For many of the 24,000 people here this week, the choice is clear.

“This is the first time the financing seems achievable,” said Diane V. Havlir, co-chair of the conference. “If we have an investment surge now, the costs will go down in as soon as 10 years.”

Former president Bill Clinton delivers closing remarks at the International AIDS Conference at the Walter Washington Convention Center in Washington, D.C. (Chip Somodevilla/GETTY IMAGES)

Former president Bill Clinton, whose charitable foundation has been a major force driving down the price of life-extending antiretroviral drugs, said maintaining momentum is the most important thing.

“Sometimes you have to make a commitment before you know how to get there,” he said during the closing ceremonies. “If we build it, they will come. If you scale it up and it works, the money will be there to fund it.”

The argument for spending more money, which is made at every conference, is especially good now. That’s because putting infected people on antiretroviral drugs essentially prevents them from infecting anyone else. That, in turn, avoids the expense of future AIDS cases (although the people kept uninfected and alive will want and need other health care).

In one presentation this week, UNAIDS epidemiologist Bernhard Schwartlander showed what would probably happen if global spending on AIDS grew to $24 billion a year — $7 billion more than is spent by rich and poor countries together now. New HIV infections, which number 2.7 million a year, would fall below 1 million a year by 2020.

“This does look like a really good investment to me,” he told the audience. “For me, the choice is clear. Let’s pay now, and not forever.”

Another urgent priority, many said this week, is preventing mother-to-child transmission of HIV.

Such infections are almost unheard of in the United States because pregnant women are prescribed antiretroviral drugs during pregnancy. The District of Columbia hasn’t had one since 2009. Worldwide, however, 330,000 babies were born infected last year.

Slightly more than half of infected pregnant women in low- and middle-income countries get HIV-prevention drugs to prevent transmission. Many of them, however, are taken off the medicines when they stop breast feeding, because their infection is in an early stage and they don’t meet the criteria for treatment under World Health Organization guidelines.

There was much discussion this week about a new strategy called “Option B+,” in which any pregnant woman found to be infected would be put on antiretroviral therapy for life. Although the strategy costs more, it eliminates the confusion, emergence of drug resistance and personal risk that occurs as women cycle on and off HIV drugs during their childbearing years.

Malawi adopted Option B+ in January 2011. By the end of the year, six times as many pregnant women were on antiretroviral drugs as at the beginning. The number of babies born with the AIDS virus fell. Mathematical modeling predicts that their mothers will have longer life expectancies and will be less likely to infect their sexual partners.

“It’s more cost-effective in the long run,” said Priscilla Idele, a Kenyan woman working with UNICEF, which is promoting the strategy.

While there are more ways to spend money, there are also more ways to save it.

A study by Clinton’s foundation, announced last week, found that in four high-prevalence African countries, a year’s worth of treatment costs about $200. Less than half the expense is for antiretroviral drugs, a fact that would have been inconceivable a decade ago.

New savings will be possible in AIDS care in the United States as two commonly used drugs, lamivudine and efavirenz, go generic this year. (The first already has.)

Rochelle Walensky, a physician and AIDS researcher at Harvard Medical School, said that $920 million could be saved per year if people on efavirenz started also using lamivudine in their three-drug combinations. In all, about 150,000 people would have to switch to generic formulations.

That switch would force many patients to take more pills per day — an inconvenience that could have health consequences if many of them ended up skipping doses.

Clinton spoke at length about using money efficiently and proving that interventions are working and worth further investment.

In two African countries where 30 percent of new infections are driven by high-risk populations, less than 1 percent of prevention dollars were spent on those at-risk populations, he said, without identifying the countries.

“We must target the money we are spending more effectively, especially in prevention,” he said.

He also said there needs to be more transparency about how dollars are spent.

“This is somewhat controversial, but we need a new level of openness about how every last dollar is spent by countries, donors, and NGOs. How can you expect program managers all over the world to make the smartest decisions if they are trapped in a financial black box?” he said.

Clinton singled out Malawi’s leader, Joyce Banda, for her “wisdom and strength” in deciding to require that all pregnant women get antiretrovirals through their pregnancy and after birth “before she knew how she was going to do it or pay for it.”

If Malawi isn’t waiting, he said, “how can the rest of us wait?”

Called AIDS 2012, the conference drew nearly 24,000 participants from 183 countries. The week-long program featured 194 sessions covering science, community and leadership. The conference was supported by almost 1,000 volunteers from across the United States and from other countries.

By Friday, it was winding down.

There were fewer scientific sessions than in any previous day. Crowds were smaller. Delegates sat down to eat lunch rather than gulp sandwiches on the run. Some posed for photographs with artwork in the convention center with new friends, and with old ones memorialized in the AIDS quilt hanging in Session Room 1, the main conference hall.

Many of those attending AIDS 2012 said they were encouraged by what they heard, but were unsure whether the goal of an “AIDS-free generation” could be reached. Especially controversial was whether limited funding should be used on a controversial new treatment tool that would give antiretroviral medications to HIV-negative people at high risk of getting infected.

“Who’s going to decide who will get it? How will they access it? And who will pay for it?” asked Nicholas Alvarado, who works at San Francisco State University’s Health Equity Institute, which conducts policy research and community training. There is also the question of how people would get chosen in a way that does not stigmatize them further, he said. The approach should be to explain that a need for the treatment tool exists in their community, and “not because you’re a bad person” because you use injection drugs, he said.

Although effective medical treatment is available to allow people to live a normal life and cut the risk of transmission by 96 percent, only 25 percent of those living with HIV in the United States have their virus under control, according to new data presented Friday by the federal Centers for Disease Control and Prevention. “There are major obstacles to making these medications really work in the population,” said John Weiser, a doctor and epidemiologist who works in public health. One in five Americans don’t know they are HIV-positive, and of those who know their status, only half are consistently in care, he said.

Without a safety net, many of Weiser’s patients have to make the choice between health care and housing, or between health care and food.

“We need to improve the safety net so people have access to these increasingly effective treatments,” he said.

Some foreign delegates said they are taking home practical advice learned from workshops.

Lungile Mabuza, 31, counsels HIV/AIDS patients in her native Swaziland, one of the African countries with high infection rates. This week, she learned two useful tips for her job at a clinic where she is in charge of keeping infected patients on their medications. Make sure the clinic provides food “for the people who take medication with their food.” Make sure HIV-positive mothers who breast feed keep taking their medications until they stop nursing.

Mabuza, who is HIV-positive, said she became infected when she was 21, when she had sex for the first time with her then-boyfriend. She is on antiretroviral therapy and has two children. Neither of them is infected.

The next international AIDS meeting will be in Melbourne, Australia, in two years.