You make the assumption that the retailer who is currently selling a product for $100, will be happy to only get to keep $70. This is illogical. The retailer will continue to want to receive the same amount of money for his product, and, in order to do so, will raise the price so that after the tax, he still makes his $100.
I disagree - it is the case today that things sold for $100 only let the retailer keep about $70. That's due to the income taxes of every link in the production chain being in the price of the good. That's because the employer payroll taxes of every link in the production chain are in the price of the good. That's because the compliance costs of every link in the production chain are in the price of the good.
When the item gets to be sold at retail, the production costs of the good are 20-25% less than the price - as the price is inflated by the fed tax costs. When those tax costs are eliminated, the retailer can charge that much less and still make the same profit.
So I disagree with your assertion - I say the retailers will be able to make the same profit while they sell for less - due to the elimination of tax costs which are currently hidden in prices.
You made a faulty assumption. I was not discussing a product that is $100 today selling for $100 tomorrow and the retailer only keeping $70. And I actually made a mistake, they would keep $77.
The use of $100 was for ease of math.
Though under the FairTax it is very likely that a $100 product today will cost $100 after tax under the plan.