And what exactly, in your opinion, would make it a fair "exchange"? In your opinion, is it even possible for such an "exchange" to ever be unfair as long as the tax laws are democratically enacted?
Sure. That's why we have court systems (and things like fundamental rights). "Democracy" in its pure form often means tyranny of the majority, two wolves and a sheep voting about dinner --- or to use a more historical example, two whites voting about how much tax blacks should pay in order to vote.
Any person has standing to challenge the fairness of a tax policy in court, either on the grounds that it violates a right of his (such as discriminating on the basis of a prohibited category such as race) or that it simply makes no sense -- in legal terminology, that it has "no rational basis." A current example of this is an attempt by some Texas towns to tax strip clubs to pay for programs addressing violence against women. The government is then forced to defend the legitimacy of such a program in court.
The strip clubs argue, first of all, that exotic dancing is a protected activity (under the First Amendment) and cannot be the basis for a tax. (That's the first argument above.) The second argument is that there is no rational basis to link violence against women specifically with strip clubs -- there's no reason to believe that strip clubs cause or contribute unduly to such violence. The courts have not yet responded, so I don't know how that case will go.
But let me turn it around. Given that violence against women is a real problem that the government should address (even the Libertopians agree that protecting people from violence is a legitimate government activity) and that it's not free, how should such a program be paid for?
Or, to put it another way, what do you think is a "fair" way of paying for such a program?
