Price increases appear even higher for smaller companies that have less leverage over suppliers. Robert Vogelbacher, the president of Men of Steel Rebar Fabricators, a 14-year-old Pennsylvania company that cuts and shapes rebar for Manhattan apartment buildings, said his prices have gone up 35 percent since the spring.

That increase cannot entirely be attributed to tariffs, but Mr. Vogelbacher said that forcing more steel buyers to compete in the domestic market has driven up costs. He added that about 60 percent of his steel had previously been bought from American companies, and that he expects that figure to grow. “You’ve got to get steel, even if the prices fluctuate,” he said. “You’ve still got to feed your customers.”

In his talks with construction managers who handle projects for developers, Mr. Vogelbacher learned that he was expected to shoulder some of the extra costs. His portion will be about half the total, he said, meaning the developer will have to swallow the other half. And that New York-bound half, he said, could wind up on the price tag for a new condo.

To cope, Men of Steel stocked up on inventory before prices started to rise. Mr. Vogelbacher is also putting off new orders as long as possible, he said, with the hope that the Trump administration reverses course.

“It’s a very scary and very weird time,” he said. “I’ve never seen anything like it.”

Higher prices might not hurt a mega-developer with deep pockets and the ability to get a discount through bulk purchases. But a smaller, less-capitalized player with thinner profit margins may have no choice but to pass the increases along to buyers, said Christopher Mesbah, the owner of Newark-based CM & Associates Construction Management. His firm’s recent work includes a pair of Manhattan luxury condos, 121 East 22nd Street in Gramercy, from Toll Brothers City Living, and Steiner East Village at 438 East 12th Street, from Steiner NYC.

“Everybody wants their profit margin, and everybody tries to maintain that margin,” Mr. Mesbah said. “But costs are being passed on, and eventually they will be felt.”