That's why I focus on total healthcare costs, rather than focusing on just one aspect (e.g., premiums, deductibles, copays, out-of-pocket expenses, etc.) In an unregulated market you could theoretically offer a health insurance plan that has a $99 deductible and a provision that voids the policy once you've had $100 of healthcare expenses. You could charge $2 for the policy and still make money on it, since it will never pay out more than $1. And that $2 policy would greatly reduce the average premium, even though the policy would be worthless.
That's obviously an extreme case, but it's just to illustrate the principle. Before Obamacare, we had predatory insurers that offered up policies that were effectively worthless, once you read the fine print. Basically, they were the Trump University of policies: a discount cost for something that isn't worth the paper it's printed on. Obamacare set standards for insurance, which weeded out the snakeoil policies. That exerted upward pressure on average premiums. Yet, surprisingly, even with that, average premiums have risen slower than normal. But, more importantly, total healthcare costs have risen MUCH slower than normal.