To me, the popularity of these ministries stems from the same concept that drives the popularity of crypto: the concept that any sort of government regulation is bad and does nothing more than add costs and let the government interfere in your life, and that unrestricted private industry can do better for less. Until you get screwed and realize that government regulation does, in fact, provide something of a backstop to protect people.
A health-sharing ministry is basically a voluntary agreement to pay for some health care costs (just like crypto is a voluntary agreement to pay money*). I would absolutely expect expect any health-sharing ministry to be much cheaper than health insurance, because:
-- The ministry can choose not to pay, whereas an insurer cannot
-- The ministry can ignore legal requirements like coverage for pre-existing conditions, whereas an insurer cannot
-- The ministry can shut down or cut off claims if it doesn't have sufficient funds, whereas insurers are required by state insurance boards to maintain sufficient funds to maintain their right to do business in the state, including often paying into state funds to cover citizens left hanging if an insurer goes bankrupt.
-- If a health insurer violates these various requirements, it's subject to criminal prosecution by the state attorney general. If a ministry doesn't live up to its promises, you get to personally sue them for breach of contract, at your own expense, and hope they have some assets left if you win.
Yes, the US healthcare system sucks. Yes, health insurance companies are often bloated and evil. But healthcare ministries don't solve these problems; they just strip away the (already insufficient) protections you get from federal law and state regulation and oversight. A better approach would be to try to strip the profit motive out of healthcare. To me, medical care is a fundamental human right, and so companies that choose to work in that field should not be prioritizing profits over service. And the religious organizations that now dominate hospital care in many areas should not be able to impose their private religious beliefs on the general public that is relying on them for service. But that's another post. . . .
*The "full faith and credit" of the US government still does actually mean something -- there's a reason the US Dollar has been the preferred currency of many struggling countries for a very long time.