OK, You can claim your RoR on the interest rate you would have paid- I'll give you that, but it you pay off your house, and the value goes down, like a lot of houses have lately, you lost money on a sale.
If you have the money in a side account making money, and your house value goes down and you sell, you are not out as much because instead of tying up the money in a depreciating asset, you had it making money on the side.
If you have the money in a side account making money, and your house value goes down and you sell, you are not out as much because instead of tying up the money in a depreciating asset, you had it making money on the side.