8 of the craziest perks we've seen in luxury real estate listings

It turns out that convincing billionaires to invest millions in luxury real estate is not the easiest sell.

In big cities across the US, glass skyscrapers and sprawling spec homes that broke ground to fanfare just years ago are now standing with empty units left to sell. Some have said there has been a slower influx of foreign capital thanks to economic instability abroad. Meanwhile, stricter regulations on all-cash, anonymous real-estate purchases - a favorite of foreign investors - have been introduced, potentially throwing some cold water on the luxury real estate boom of recent years.

As demand for multimillion-dollar properties has fallen in recent months, developers are leaning increasingly on flashy extras to attract buyers. Here, we've rounded up some of the most extravagant perks we've seen lately.