The discussion has always been about the price of new homes falling with the removal of the income tax so your trying to misstate what has been sense is just more of your purposeful misdirection activity.
Even used homes would benefit from the FairTax though, as mortgage rates would decline making even used homes easier to afford,
Since you've demonstrated you don't "do numbers" I'll not give you any to avoid further confusion on your part - you're already confused enough..
So, what you're saying is that only the price of older homes is influenced by supply and demand, new homes are priced using a defined profit regardless of the market.
Both my grandfathers were contractors, that would have surprised them to hear.