FromTexas
This Space for Rent
No the math works every time, you run the numbers and go with the best economic choice every time and there is no argument which is best. Anything else is just opinion.
Really?
Let's take your example.
$200k/6% ($350k home)
Trading down to $150k mortgage/6%. ($280k home - $50k less equity on mtg with $20k reduced equity from selling home)
You are trying to convince the person to take less, so lets says you want it for $20k less.
The person is saving $250 a month on interest using your simplified interest from your original post; which is fair since their savings on interest will be slower than the higher payment. We will stick with your basic assumption that principal will be recovered in this trade down.
The person can reinvest their $40k... at 5% guaranteed. So, $2000 a year. It will take them about 30 months till they will start gaining after recovering the reduced price in your scenario; only by providing you a generous reduced principal per month payment. If you are talking saving $30-$40k over their current price, it will be quiet a bit longer.
So, they have to decide if in 30 months someone will offer them their asking price. Probably more like 3 years.
But... I fully agree someone should do the math and find out what is better for them economically (sometimes it will go as you suggest and sometimes it wont), and I have no problem with suggesting people trade down who can't afford their payment, need lower costs for other reasons (approaching retirement), etc... People don't spend enough time looking at the impacts of what they do. I also appreciate you suggesting they are moving into owning at a better economic circumstance than they currently have. In the end, it shows you recognize the value of ownership.