I think the cost sharing is less well known than the premium subsidies.
This article gives a good summary of the financial aspects of ACA plans.
If you have an income under 400% of the poverty level, you get a premium subsidy valued at enough to make a silver plan have a net cost matching a certain sliding percentage of your income. Most people know about this. The particulars are described in Table 2 of the article I linked.
The cost sharing is an added benefit only available to households with income between 100-250% of the poverty level. Normally bronze plans have an "actuarial value" of 60%, meaning the plan will pay for 60% of the average person's medical bills. Silver plans have an actuarial value of 70%, and gold plans have an actuarial value of 80%. But for people in the right income group, silver plans have to raise their actuarial value to as high as 94% (details in Table 4). They way they do that is by lowering deductibles, out-of-pocket maximums, co-payments, co-insurance, etc.
The result of this is that the net monthly premium can be very low because of the premium subsidies and the coverage level can be even better than a gold plan due to the cost sharing requirements.
To illustrate how big of a difference income can make, I did a quick comparison on Washington state's exchange website. I looked up rates for a 30-year-old married couple.
At $40k income (just over 250% of the FPL), Premera's "Silver 2500" plan has a $5,000 family deductible, $8,200 out-of-pocket maximum, and 20% coinsurance, for a $343 monthly premium after tax credits.
At $30k income (just under 200% of the FPL), the same Premera "Silver 2500" plan has a $1,500 deductible, $2,300 out-of-pocket maximum, and 20% coinsurance, for a $218 monthly premium after tax credits.
At $22k income (just over 133% of the FPL), that same plan has a $500 deductible, $1,000 out-of-pocket-maximum, and 20% coinsurance, for a $132 monthly premium after tax credits.
The $40k income couple might have to pay as much as $8,200 + ($343 * 12) = $12,316 in the worst case.
The $30k income couple might have to pay as much as $2,300 + ($218 * 12) = $4,916 in the worst case. (a $7,400 cost difference for a $10,000 income difference!)
The $22k income couple might have to pay as much as $1,000 + ($132 * 12) = $2,584 in the worst case. (a $2,332 cost difference for an $8,000 income difference)
That seems like a mighty strong incentive to keep one's income below that 200% of FPL line during retirement if at all possible.