According to FairTax lore, these people pay 22-23% embedded taxes on every purchase they make at retail right now. It is hidden in the cost of the good or service, but if the shadow people didn't make the purchase the thing wouldn't be made and the tax wouldn't get paid to the FedGov.
The prebate is a monstrosity that will do more to foster government dependence and put people at the beck and call of politicians than anything imagined by Marx. And future pols would tamper with that for class warfare, vote-buying reasons-- you can be sure of that.
Excellent point!