Evolutionary psychologists would most likely explain females' greater emphasis on potential mates' economic resources by suggesting that it: increases females' confidence about the maternity of their children increases the likelihood of survival for their children supports their innate need for a large territory allows them to acquire a greater variety of time-saving appliances

I believe the answer is: increases resources available for their children.

This could even be seen in modern day mate selection. When you observe it, you would notice that men with 'high power/influence' tend to have the largest option in term of selection. This happen because high power/influence is usually correlated with ability to obtain large amount of resource (wealth/connections)