Mr. Honig and his business partner and wife, Stephanie, have spent a decade wooing that clientele, making a trip a year to China to pitch sommeliers in top restaurants and hotels. He has recently expanded beyond the obvious stops in Beijing and Shanghai, visiting cities like Guangzhou, in southern China.

“There are people who want to spend the most, but there are also aspirational buyers,” Mr. Honig said. “You may want to buy the Rolls-Royce, but you can afford the Mercedes.” And that’s his sweet spot.

His most popular cabernet goes for around $25 a bottle wholesale, and he sends more than 500 cases of it every year to a plucky Shanghai importing business started by two brothers with dual citizenship. With existing tariffs and value-added taxes mixed in, the total charge tacked on to California wine was already close to 50 percent. After the importer factors in shipping, takes its cut and passes the bottles to a hotel or retail store, which takes its cut, the Napa red ends up selling for the equivalent of around $100.

An extra 15 percent charge would be brutal. “No one wants to overpay,” Mr. Honig said. “If all they’re looking at is two different bottles side by side, and we are competing with Australia and Chile, that’s a big competitive disadvantage.”

Chilean and New Zealand wines face no Chinese levies, thanks to free-trade agreements. Australian bottles will enter the country tariff-free next year.

Larry Yang, an importer in Shanghai, said his customers liked California wines, but not enough to ignore an even higher price tag. The wine isn’t cheap as it is, he said, and if it gets pricier, he will look elsewhere.