The former The Hills stars ended up broke after blowing a massive $10 million (£6.2 million), fearing they had to spend money before the Maya-predicted Apocalypse in December (12).
The couple has now opened up about how they managed to lose so much cash, revealing they spent a fortune on designer clothes, private jets and gold bars to hand out to their friends, as well as $3,200 (£2,000) bottles of wine, penthouse hotel suites, security guards, make-up artists and stylists.
Pratt even bought a $96,000 (£60,000) rock to decorate their home as the pair desperately tried to set themselves up as rivals to superstar showbiz couple David and Victoria Beckham.
He tells Britain's Ok! magazine, "I bought a £60,000, 1,500 lb quartz crystal from a volcano in Peru - I needed a crane to put it in our house. In hindsight, that was a little excessive... When we came into all this money, we just couldn't spend it fast enough. I just lost the plot... When you start buying people cars and you're not David Beckham, you're heading for trouble...
"I spent over a million dollars on men's clothing because I wanted people to take me seriously as an A-lister. I wanted to be in the fashion magazines alongside Brad Pitt."
Montag adds, "I grew an obsession with Hermes Birkin handbags. They were like £13,000 each. I had wardrobes full. But we wanted to keep up with the Beckhams. I love Victoria's style."
They also lost $2 million (£1.3 million) by setting up their own record label to launch Montag's flop singing career.