I know this has been pointed out to you numerous times, but surely you realize that $200,000 price on the house has built into it all the hidden taxes the builder paid during construction plus their profit.
So, you could be paying $16,200 sales tax on the same exact house that now costs only $180,000 assuming only a 10% decrease in retail price even though many studies show the tax burden on products is as much as 40%.
You repeatedly ignore COGS (Cost Of Goods Sold), but I can tell you this, businesses don't ignore it. You assume that all retail sales entities will conspire to not drop prices based on their lower COGS. You assume no business will lower prices to make a market share play. Yet, in reality, businesses do this all the time.
Also, don't forget the income and withholding taxes you currently pay on the portion of your income used to pay the principal on that $200,000 house.
Even combing the 9% sales tax with the 9% flat tax on income Cain is proposing, the ultimate cost of buying a house would be less under 999.