Why I'm overpaying my mortgage every month

When does a $310,000 house cost $642,000? It's not a trick question - for Andi Camp, the bigger figure is what her home really costs, once she accounts for the interest she'll pay over the course of her 30-year mortgage."I don't think people realize how much interest costs," says Andi, a 35-year-old engineer in Portland, Ore. "I paid more than $14,000 in interest in 2009. That's a lot of freakin' money."

Too much, as far as she's concerned. So every month, instead of making the basic payment, she adds an extra $72. She doesn't miss the cash, and over the life of the loan, she'll save more than $35,000. Add another $1,000 or so a year from tax refunds and bonuses, and she'll save an additional $30,000 and pay off her mortgage five years early.(To run your own numbers, check out thismortgage paydown calculator.)

How did Andi wake up to the price of interest? When she worked as a musician, singing and playing bass and piano, she racked up $5,000 of credit card debt. Then grad school beckoned, and Andi saw an opportunity: By consolidating the balance from her credit cards into her student loan payments, she cut her interest rate from 24 percent to 6 percent. Lesson learned. "If price tags included interest, maybe people would think twice," she says.