Free gift with purchase: Buy a penthouse, get a Lamborghini

When you order a burger, the kid behind the counter asks, "You want fries with that?"

When you open a bank account, they give you a free toaster.

And when you buy certain luxury apartments in Dubai? Why, then your real estate agent will hand over not one key but two: one for your new home, and one for your new car.

Damac Properties' gift-with-purchase even comes in combos of different sizes. Less square footage will get you a free Mini Cooper. Tack on a bit more and Damac will upgrade you to a nice BMW.

Or you can super-size it! Buy yourself a penthouse, and Damac will throw in a Lamborghini Aventador Roadster -- which "supercar" costs $445,000 and is "like a hit of atropine mixed with kerosene," the redoubtable race car driver Alex Lloyd of Yahoo Autos informs us.

Of course, such a "gift" doesn't come cheap. A qualifying four-bedroom penthouse will set you back $15 million, the New York Daily News estimates.

Select Damac Maison "luxury serviced hotel apartments" at the Distinction and the Upper Crest in the Burj area of Dubai -- home to Burj Khalifa, the world's tallest tower -- are eligible for the promotion, the company says in a news release. Units at Dubai Marina's Damac Residenze, with interiors designed by Italian luxury fashion brand Fendi, also qualify, according to the news release.

The promotion runs alongside the Dubai Shopping Festival, Jan. 2 to Feb. 2.

So hurry!