I really think you have a fallacy of logic here. You don't have to pay income tax on it because you already have. You are esentially comparing your $50,000 income (having already paid tax on it) to someone making $50,000 before taxes and saying that your money is worth more. This is not a valid comparison. A valid comparison would be comparing your $50,000 which you have already paid tax on, to someone who made $50,000 after taxes. And the value of those monies are the same.
Where there IS an inequity is where your neighbor has his savings in a tax-deferred account, and will benefit from escaping taxation on it's balance when the FairTax is implemented. HE will have more value for his income than you will, because yours will have been taxed and his will not have been. This is an inequity in the existing system, as you have already paid taxes on your savings, and your neighbor has postponed it, to the point where he doesn't even have to now. The FairTax has no bearing on this inequity. If you both went and withdrew your balance and ran to Mexico never to return, the same inequity would exist.
"...It's not just the absolute dollars I have or the taxes that I pay, it's how it compares to what others have and what taxes they pay. That helps establish what my dollars are really worth...."
That's absolutley correct and speaks directly to my previous post, wherein I said: "The ball to keep your eye on here is total purchasing power."
You seem unconcerned by the fact that your investments are suffering reduced ROI as a result of the current system of taxation. That impacts your ability to consume in an invisible way that is impossible to accurately quantify. Moreover, 15.3% of your wage is being confiscated as FICA / Medicare taxation, and the government has no obligation whatsoever to return any portion of that to you. If you are concerned about your standard of living while in retirement, those two facts should cause you great concern. The FairTax eliminates both of those impediments to your ability to provide for your retirement.
Because the FairTax is calculated to be revenue neutral, it will by definition take NO MORE MONEY from the economy than the current system. The difference between the two systems is that in our current system, the taxes that you pay are invisible and unquantifiable in gross total. Under the FairTax you will not suffer a degredation in your total purchasing power, but you will be able to calculate your total tax burden because the tax will be fully visible.