The assumption here about fairness is inaccurate. In his example, all the men receive the same benefit, the beer, regardless of how much was actually paid by the individuals. In the real-world, outside of the simple example laid out here, the social benefits received by the wealthy far outstrip the benefits received by the poor. A more appropriate analogy would be that there are three bars: 1) Where the poor go - it's crowded, dirty, and the beer is of very suspicious quality (read inner city schools)
2) Where the middle-class goes - not so crowded, but always in danger of being pushed down the ladder
3) Where the wealthy goes — a very nice place indeed.  In this example, the wealthy receive the same level of benefits, but are actually paying less. In short, it is laughable to assume that all the men receive the same level of benefits regardless of what is being paid.