In this light, laissez-faire capitalist economy as "liberal" makes sense: sure people are selfish and want to consume, but they can be trusted not to collude or undermine the system. Because people are trustable, laissez-faire can regulate itself, without governmental intervention. Neo-liberalism is the revitalization of this free-market mentality.
(Of course, current definitions of "liberal" and "conservative" have shifted substantially from these roots. Conservatives in the U.S. support neo-liberalist policies such as deregulation, privatization, cutting social services, no unions, and reign of the free market, while liberals advocate increased governmental involvement and support.)
In the original sense, I'm conservative in terms of economics, because it seems that people do collude to undermine the system, and the government does need to intervene to prevent it. Of course, the problem is that we can't trust the government not to collude as well. And I will concede that if everyone followed the neo-liberalist ideal, rather than first-world countries forcing others to do it but not doing it themselves, a free market might work ...