Comrie's dad is the founder of a Canadian appliance and furniture empire, worth an estimated $500 million.
"It was a totally amicable agreement," an insider says. "They love each other very much and knew this was just a technicality."
Duff, 22, and Comrie, 29, who met at an Idaho resort, have dated since 2007 (before he popped the question earlier this year).
While dating Duff, Comrie wasn't shy about dropping bucks.
Shortly after they began seeing each other in 2007, he surprised her with a Mercedes-Benz G-class SUV as an early 20th birthday gift.
Duff's engagement ring also is worth a reported $1 million.
Despite his money, Duff told UsMagazine.com they have a surprisingly "natural" relationship.
"We both have busy jobs, and we're both very focused people, so that helps," she told Us. Said Comrie, "We have fun. We both live such different lives, but it's always fun to support each other and spend time when we get to."