If you offer it, will they come? Insurers and some U.S. senators have proposed offering cheaper, skimpier ?copper? plans on the health insurance marketplaces to encourage uninsured stragglers to buy. But consumer advocates and some policy experts say that focusing on reducing costs on the front end exposes consumers to unacceptably high out-of-pocket costs if they get sick. The trade-off, they say, may not be worth it. Coverage on the health insurance marketplaces now is divided into five types of plans that require different levels of cost-sharing by consumers. All the plans cover 10 so-called essential health benefits, including hospitalization, drugs and doctor visits. Preventive care is covered without any cost-sharing.