That means that a Republican health reform plan that is both cheaper and better than Obamacare will be hard to deliver.

Republicans in Congress and right-leaning think tanks have put together a number of possible Obamacare replacement plans. They are all slightly different, and it is unclear which one Mr. Trump and congressional leaders will choose. But none of them solve both sides of the “less expensive and far better” equation.

Most of the G.O.P. plans manage to be less expensive for the federal government — by offering stingier federal payments in helping people buy insurance and allowing the coverage people buy to be skimpier. But those proposals will tend to increase, not decrease, the amount many Americans spend on their health care.

Lower-income people will end up paying a larger share of their income to buy coverage than they do under Obamacare. Deductibles and other forms of out-of-pocket spending, capped under Obamacare, will tend to rise in many plans. Millions to tens of millions fewer Americans will have coverage under such plans, according to independent estimates.

Republicans also want to pare back the minimum package of benefits that plans must cover, which will drive up costs substantially for some patients, while reducing them for others. If the bill eliminates requirements to pay for maternity care or prescription drugs, for example, that could lower the sticker price of a health plan, but will make health care much more expensive for anyone who has a baby or takes medication.

There will be people who will be better off under a Republican plan. Higher-income, healthy people who buy their own insurance have been the most disadvantaged group under Obamacare, and their fortunes would improve. The Republican plans, with their skimpier benefits, and more generous tax assistance for the wealthy, would offer them a better deal.

The G.O.P. plans tend to be worse for people who need insurance and are poor or have major health problems. (Some sick people may be far worse off. Mr. Trump has promised that people with pre-existing health conditions will be covered under his plan, but not all the Republican plans offer them the kind of coverage that they can get under Obamacare.)