Lady Gaga just hit the jackpot.

The six-time Grammy winner will begin a two-year Las Vegas residency at the new Park MGM resort in late 2018 — and Variety reports that the “Million Reasons” singer is guaranteed just over $1 million per performance. Considering that she is committed to 74 appearances, this could bank her almost $100 million when merch sales and other bonuses are applied.

Sin City residencies have been big business since Frank Sinatra and Elvis Presley held court in the 60s and 70s, and they’re getting an encore as pop stars like Britney Spears, Jennifer Lopez and Mariah Carey have hit the Strip.

Spears’ four-year “Piece of Me” residency at the AXIS Theater at Planet Hollywood Resort & Casino, which closes this New Year’s Eve after 249 performances, has earned the “Gimme More” singer more than $130 million in ticket sales, with another $5 to $6 million expected before it wraps.

Britney Spears playing at Planet Hollywood Las Vegas. (Denise Truscello)

Lopez, who also played the AXIS, raked in $1 million during the 2016 leg of her residency, and just announced the final stint will run June 13 through Sept. 29, 2018. And the expanding nightlife and EDM scene is giving DJs such as Calvin Harris and David Guetta $400,000-a- night gigs.

But in the 80s and 90s, playing Vegas was see as a swan song for the sellouts and the washed outs. “There used to be a certain element of cheesiness to playing in Vegas,” music journalist and former New York Daily News columnist Jim Farber told Moneyish. “I talked to Cher about that, and she referred to it as an ‘elephant graveyard where talent goes to die’ – and she was speaking of herself.”

So what put Vegas on a winning streak to becoming a million-dollar draw for pop stars like Lady Gaga, who boasts 30 million albums sold worldwide, almost 30 million Instagram followers and 75 million Twitter followers?

Thank Celine Dion for ensuring that Vegas residencies will go on.

Celine Dion performing in Las Vegas in 2015. (Denise Truscello)

“It really goes back to over a decade, when Celine Dion launched her residency at Caesars Palace – and that was really the beginning of top notch artists starting residencies in the height of their careers,” Jason Gastwirth, senior vice president of marketing and entertainment for Caesar’s Entertainment Corporation, told Moneyish.

The “My Heart Will Go On” singer’s four-year “A New Day …” residency grossed $382.5 million. “We’ve seen major success with these, so the idea that this is something that would be a detractor to their careers is past,” said Gastwirth. “This is just another aspect of touring now.”

Las Vegas is also skewing younger, with Millennials making up one-third of all visitors last year, up from being only one-fourth of them in 2015, according to the Las Vegas Convention and Visitors Authority. And that’s lowered the age of the average visitor to 44. It was 51 as recently as 2013.

And these newcomers are showing more interest in catching live acts, trying new restaurants and exploring the city than they are frequenting the casinos, which is also fueling the residency boom. Twenty-four percent of overall visitors saw a headliner last year, up significantly from 14% in 2012 and 13% in 2013.

Jennifer Lopez performing at Planet Hollywood Las Vegas. (Denise Truscello)

Plus, as it’s gotten harder to earn a living in the music industry as audiences stream music instead of buying albums, Farber says performers (and their fans) are less picky about where they get paid.

“We don’t criticize artists for doing TV commercials anymore. Those kind of ‘sellout’ accusations are antiquated in a world where we have all accepted that it is difficult to make money in music — or, we have just accepted the greed,” said Farber. “So residencies have become very popular with certain performers because, first of all, they can pay them tens of millions of dollars.”

Finally, there’s more than money at stake here. There’s also sanity. Touring takes a lot out of entertainers. So being able to plant themselves in one place – such as Gaga and Britney in Vegas, or Billy Joel’s extended NYC residencies at Madison Square Garden – lets them get some rest and spend time with their families between shows.

Gaga’s residency comes on the heels of a rollercoaster year that saw her play the Super Bowl halftime show in February and release a documentary on Netflix — but health problems have plagued the tour for her latest album “Joanne,” such as canceling her Rio de Janeiro dates. So parking in Vegas for two years may be just what the doctor ordered, even if she has committed to 74 shows.

“It cuts down on the wear and tear,” said Farber.