In September 2013, Britney Spears spent $100,000 to elaborately announce her career comeback  a two-year residency at Planet Hollywood Resort and Casino in Las Vegas.

That December, Spears took the stage to debut her new show, titled "Britney: Piece of Me."

Spears' original 2-year contract reportedly had her earning $30 million to perform 48 shows per year. With ticket prices at $60 to over $500, the residency has been so successful that in September, Spears announced she had extended her contract for an additional two years through 2017.

While Spears' most recent album "Britney Jean" was a total flop, the singer's Las Vegas residency has been a huge win for Planet Hollywood. Citi credit analyst Jenna Giannelli explains in a new research note:

Planet Hollywood The property is doing very well, having been revitalized by the Britney Spears show. Prior to her contract, the company had EBITDA of ~$80mm that is now run-rating near $100mm. Her contract expires at the end of 2015, and the company is already engaging new acts to keep the momentum going. Further, as capex wraps up on the Quad, it will be reallocated toward properties that need refreshes including Planet Hollywood, whose rooms and pool need upgrades.

In other words, Spears can take at least some credit for boosting Planet Hollywood's annual operating earnings by around $20 million. Note, this is the money the house keeps after paying Spears.

The resort and casino was taken over by Caesars Entertainment in 2009 after the casino defaulted on its mortgage.

As someone who has watched Spears lip-synch her way through the Vegas show, Planet Hollywood should consider itself lucky that people will still pay to see pop's one-time princess.

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