That's a good point. How much was your present $650K house worth back in 2008?
In regards to the convo as a whole.
I do believe paying off your house is good. In the end, it's all equity, so if you can pay off your house cash, sure go for it, but I wouldn't.
The person that referred to the 25 year old that lost everything probably invested 100% or more, of the equity of his home into Wall Steet. That is a bad, stupid and horrible idea.
I would suggest taking a remortgage of half the valued amount, and reinvesting it.
A big thing is colleges. Kids, either through financial aid or well set, will pay a decent amount of cash to rent out a house with a few buddies. With 325,000, you could easily buy 4 houses (80k per) that are VERY close to MSU. A little bit further away and you can buy houses from 35,000-65,000. Anyway, you could rent these houses out, that on average have 3 bedrooms, at least 500$ a person, but the renter will pay for whatever utilities.
That's ((3*500)*(4)) = 6,000! Put 2,000 on the side for taxes, rental license, insurance, etc. 4,000!
Considering minimum monthly payments would be around 500 for each house, I would put 2,000 on payments (500 per house), and 500 I would convert it to short-term, cash ready equity via the market (stocks), put 500 towards the mortgage, and the 1,000 towards a mix of paying either mortgages off, and saving the rest for a down payment on a new house to rent out.
In 4.5 years, you could pay all of the mortgages off on your rental houses, so you would have 6,000$ coming in a month, with just your original mortgage, plus 4 houses that have a combined equity of over $300,000.