They weren’t invited to the Second Avenue Subway’s gala New Year’s Eve opening party, but Upper East Side business owners and residents were celebrating on Saturday anyway.

“I’m ready to make a living again!” cheered barber Emin Cekic, 50, whose Second Avenue shop is near one of the new 72nd Street subway entrances — and was nearly forced to close because of the seemingly endless noise, barricades and detoured traffic of construction.

“It’s been really terrible for eight years,” Cekic said.

Gov. Andrew Cuomo debuted the $4 billion first phase of the long-awaited subway line Saturday night at a cocktail party and inaugural ride set to be attended by Mayor Bill de Blasio and sundry state and city officials, along with selected construction union heads and art institution bigwigs.

“They should have invited all of us,” Tina Schneider, 60, quipped of her fellow long-suffering Upper East Siders.

The new line stretches, for now, from 63rd Street to 96th Street, with new stations at 72nd, 86th and 96th streets. Riders will make some 200,000 trips each weekday.

Phase 2, which won’t begin construction for at least two years, will extend the line up to 125th Street in Harlem, with stations at 109th, 116th and 125th streets.

The new stretch of subway will go a long way to relieve crowding on the 4, 5 and 6 lines along Lexington Avenue.

Sheila Xie, 50, pointed to the dirty awning of her store at Second Avenue and 72nd Street, Wo’s Custom Tailoring, as proof of how messy construction had been. “Since the street has been cleared, there’s already more customers coming in,” she said.

The Lexington Avenue line has been the only subway serving the Upper East Side since the 1940s, when elevated lines along Second and Third avenues were taken down.

“The train was so close to the buildings,” Stan Chaitan, 91, remembered of the Third Avenue El. “If the train wasn’t going fast, you could see into someone’s bedroom.”

At this point in life, though, the El’s long-awaited underground replacement doesn’t excite him that much.

“I rather take the bus,” he said.