The Nixon/Reagan-deregulated insurance industry is a very giant "baby" with a huge Republican-given "lollipop" of no oversight, no regulations, and no consumer protections---1300 for-profit greed-driven insurers that became an ALL-PROFITS, NO PAYOUTS system with help from the Koch-funded corporate-colluding Congressional Republicans from 1979 on through to now. The insurance lobby outnumbers our elected representatives in Washington by at least 100 to 1---all of them paid to be 100% against any attempt to take their GOP-granted "lollypop" of deregulation away from them.
And then came the 2009 election with a Democrat-controlled 111th Congress and a visionary named Barack Hussein Obama as the people-chosen new President, with a dream to get affordable health care and long-needed insurance reforms for the American people. Voila! A hard-won passage of the Patient Protection and Affordable Care Act (P.L.111-148) and its supplemental Health Care and Education Reconciliation Act (P.L.111-152), a.k.a., the Affordable Care Act or "Obama Care."
The reason the public-private approach to health care and insurance reform was pursued rather than a "Medicaid for All" approach had a lot to do with America's history of being a yin-yang balance between capitalism (for profit, privately owned...which the insurance industry had become) and socialism (taxpayer funded, people owned) which is what a "Medicaid for All" approach would have been. But the Obama Care option was also financially wise because of the Republican-caused economic devastations we were facing---the 2004-2009 collapse of our housing and credit markets that cost millions of Americans their homes and blighted far too many urban communities, thus lowering property values for remaining homeowners (putting them "underwater" in terms of borrowing power); the price-gouging on gas during oilmen Cheney and Bush years; and the nearly fatal GOP-deregulation-caused MELTDOWN of our entire financial system due to criminal behaviors of bankers and Wall Street---a MELTDOWN that took us into the worst economic recession since the GOP-caused Great Depression (1929-1938), bankrupting most of our European trading partners, thus slowing our own recovery prospects. By the end 2008 (with Republicans in totalitarian power from 2001 through to 2008), the U.S. was losing more than 800,000 jobs per month---and each job loss meant less revenues for local, state, and federal taxes; Social Security FICA taxes, and dried up consumer spending that put small businesses at risk. If we had gone for the Medicaid For All approach, putting those 1300 capitalist insurers out of business, how many more jobs would have been eliminated? This was a huge consideration in shaping the oversight and reforms for the existing insurance industry, and explains why the public-private combination of the Affordable Care Act made the most sense.
Your question is about affordability, and the insurance lobby bullied Republicans have attacked the very things included in Obama Care that would keep insurance affordable: (a) The mandatory component for well-off healthy young people who want to game the system---not get insurance that they can easily afford, but then use the more expensive ER for non-emergency with no intention of paying...passing those costs on to other consumers through higher premiums; and (b) Eliminating the ACA's state-by-state oversight panels that would evaluate any insurer's effort to raise premiums higher than the cost-of-living rates, causing an audit of that insurer to determine if there was a legitimate reason for making the excessive increase. As you can probably imagine, the spoiled-brat lollipop-devouring 1300 for-profit insurers hated both of these ACA provisions with a purple passion---and so we, the people, can actually LOBBY or DEMONSTRATE to get these cost-reducing insurers-reforming features of Obama Care put back in.
Another way to lower costs overall is to go after "Big Pharma," also deregulated by the campaign-donations-lusting Koch-backed Republicans. Look for the Presidential and Congressional candidates who have a plan to bring the multi-trillion-dollar corrupt and GOP-deregulated pharmaceutical industry into compliance with consumer protection measures. For now, the one candidate with a plan is long-time consumer advocate and economics expert Elizabeth Warren, but attend the rallies in this next year and ask the right questions of any of these candidates---get the idea of regulating the pharmaceutical industry into the platforms of each candidate, and that would be yet another way to get the health care system affordable.