The husband-and-wife team, who achieved celebrity on MTV reality series The Hills, admitted that they would change more than a few things if they could go back.
In a new interview with The Daily Beast, Spencer said, 'We were living each other's mistakes. Everything we were doing, in retrospect, was a mistake. The second we continued on our quest for fame was a mistake.
'This isn't a business. That was the big thing I didn't get: Reality TV is not a career. Anyone who says, 'Oh, you can have a career in reality' - that is a lie.'
The couple blew so much of their cash that they now live rent-free with Spencer's parents.
'I should have kept every dollar that I had,' Heidi admitted, rather than splashing out on more than 13 cosmetic procedures since 2007.
'Obviously I wish I didn't do it,' she admitted. 'I would go back and not have any surgery. It doesn't help. I got too caught up in Hollywood, being so into myself and my image. I don't regret anything, but if I could go back, I wouldn't do it.
'I thought I was investing in myself and my brand, like Kim Kardashian. When she buys these clothes, she's investing in herself, because she is a big brand and is likable. I thought I had that potential. My ego got too big. To think I could be someone like that when I was the most hated girl ever.'
And Spencer has his own financial regrets, having spent $2 million on Montag's failed music career, and an estimated $1 million on his wardrobe.
'I would never wear that again,' he said. 'They're props. Everything we were doing, we were buying props. I bought a big blue monster truck just to drive it on The Hills for an episode. Never drove it again.'
But the two live a much calmer life nowadays. 'It's like what 70-year-olds do,' Spencer said. 'We're reading a lot of books.'
'We're watching movies. I do a lot of laundry. A lot of laundry,' Heidi added. 'We're training our dogs, so I'm cleaning up less poop inside, which is great.'