The part of taxes being paaid by Joe P. are only the portion of the cascading at the level to the retailer. Taxes on the earlier cascading in the supply chain have already been paid by others but not by Joe P. He pays the retailer's cost of goods (which already have taxes embedded that have been paid by others) plus some portion for the retailer's income tax portion.
Joe P. forwards no part of the already-embedded taxes to the government (nor does the retailer); others have already done that and none of Joe P's funds go to the government for that portion. The $400 is the tax portion paid by Joe P. in the example. That is a lot less than the FairTax tax revenue that is generated.
Bzzz, wrong answer. Joe P. and the other end consumers pay all the taxes in the whole supply chain. That is how your economists come up with the 20-30% embedded tax in all the products. The way they figured those numbers is ALL taxes end up in the final product. That is their assumption, at least until that assumption doesn't fit what their point is. Like when they talk about workers, then a new assumption is born, and it is the worker who pays. But I regress into the biggest fraud of your economists, changing assumptions to overstate their case for the fair tax.