For three years running, thanks to a combination of the way the ACA's premiums subsidy formula works and the Silver Loading workaround, several million low-income people are eligible for fully ACA-compliant healthcare policies which end up costing them NOTHING in premiums after federal tax credits are applied.
Here's why: Under the ACA's subsidy formula, if you earn between 100% - 400% of the Federal Poverty Line ($12,490 - $49,960/yr if you're single), you're eligible for subsidies which bring the cost of the benchmark Silver ACA plan down to between 2.06 - 9.78% of your income, on a sliding scale.
If you earn less than 200% FPL (just under $25,000), you also qualify for heavy cost sharing reduction assistance as well...but only if you enroll in a Silver plan.
So, let's suppose you earn exactly $25,000/yr (just over 200% FPL). At that income, you'd qualify for subsidies bringing the benchmark Silver down to 6.5% of your income, or $135/month. If the benchmark plan costs, $600 at full price, you'd therefore be eligible for $465/month.