Taking the word "afford" literally, if you can only afford $50 on the first auction, and you lose the auction, then you'll have an extra $50 on the next auction, and will be able to afford $100. If you lose that auction, you'll be able to afford $200 on the auction after that. I think that the concept you're thinking of is not so much afford, as marginal utility cost. For someone with a yearly income of $200,000, a marginal util is going to cost a lot more than for someone with a yearly income of $40,000. Thus, the richer person may be willing to bid more, because the utils are worth more to that person. It is therefore more efficient (that is, it is a Pareto improvement) for the richer person to win the auction, and give money to the poorer person that the poorer person can use to buy utils elsewhere. And I really wonder at who's deciding what goes in the Google Chrome spell checker dictionary, because apparently "util" is in it, but "externality" is not.