A prefabricated home for $2.5 million? Believe it or not, not only do they exist, but the market for these modular mansions is booming.

The modular home market has catered to the high-end since the mid-80s. But lately this little-known real estate niche has exploded into a bonafide industry. Today, customers are driven by the easy customization, the "green" features (by building in a controlled environment no mold or mildew can get in the walls, etc.) and the speed of construction. And while the Lexus-driving crowd may not be prone to penny-pinching, the six-figure savings are an incentive as well!

"We're instant-gratification people," says Bob McCarrick, a 39-year-old investment banker, as he and his wife, Kristen, 39, walk the floors and touch the drywall of their 7,200-square-foot insta-mansion.

Trucked 205 miles from an assembly line in Pensylvannia, the McCarricks' home arrived in 21 boxes stacked on a fleet of semis. 32 hours later, the six-bedroom, 6.5 bath French country mansion looks close to finished.

Across the street, a house built from scratch is going up at a more leisurely pace. 

As easy as Lego's

"Without the recession, nobody would be paying attention," said Russell Versaci, a Middleburg architect specializing in farmhouses for wealthy clients who partnered with Haven in 2008. A custom home built from studs can take 18 months or longer. "When I can cut that in half, that's a thrill for people," Versaci said.

"Off the shelf" used to be a dirty word just a few years ago. "You're telling me it's okay for people in this neighborhood to see homes coming in on boxes?" asks Jim Gibson, a cusom builder who's pebble-dash brick house two doors down is under contract for $2.8 million. 

But another modular is on the way to the same neighborhood. Lee Alexander and his wife closed on a lot and designed a 5,500 sq. ft. modular with cathedral ceilings and three garages. The sticker? $2.5 million.

And from all reports, no one could look at one or the other and say it's a modular.

Times are changing for modular homes. And with these changes, times are changing for the real estate industry as well.

To see a slideshow of the assembly, click here. 

To see a time-lapse video, click here.