Irrational People - Rational Outcomes

You do not need rational people to reach rational market outcomes. See Don Boudreaux's post on Cafe Hayek.

[C]ompetitive, decentralized markets -- commerce -- generally manage to produce results that make us seem to be more rational and smarter than we really are.

Boudreaux quotes from an interesting paper,"The Market: Catalyst for Rationality and Filter of Irrationality" by John List and Daniel Millimet, winner of the 2008 Arrow Prize for Senior Economists. (Free working paper copy is available here.)

[E]ven when markets are populated solely by irrational buyers, aggregate market outcomes converge to the intersection of the supply and demand functions.

In other words, even when people act irrationally in the market place, market prices are determined by supply and demand. The prices are the same as if people acted rationally.