I think a lot of this is psychological, although there are some numbers. In our case, we got lucky; I took a University job in Houston in 1990 just as Houston and the Southwest was coming out of the Credit Union Real Estate Depression in the Southwest, which was crushing for those who experienced it.
The house we bought had been vacant for 2 years; we paid 113,000 for a 2500 square foot house with a pool and half an acre. I knew we would have to put a new roof on it soon and put in a pool heater and some fixtures, which had been stripped. The mortgage was 9.75%.
We had a 3 month old and a 3 year old, and were up against the wall until the 3 month old was close to kindegarten, when suddenly we had a huge influx of cash (little day care expenses). We refinanced down to 7.5, then took a 15 year mortgage at 5% when suddenly due to pay raises, the decrease in mortgage costs, etc, we suddenly had extra money--what a concept.
I think we paid off the house in 2007 or 2008 or so (might have been 2006 since we used a cash bonus to pay off the rest of the mortgage), which psychologically allowed the DW to agree to retire early in 2015. We had taken a second in fears we would need the cash to send the youngest to college, which--due to fortunate bonuses for DW--we never had to use.
It's quite possible we would have wound up with more money had we just stuck with the 6% 30 year, but then there was the Great Recession and the Tech crash, so it's quite possible we would have wound up with a lot less. My parents were lower middle class preacher family and my wife was from a poor Polish family just outside Philly, so I never imagined I would retire early and in (relative) luxury, perhaps not luxury compared to many here but luxury indeed, which is a state of mind.
