75% of American gamers have paid real-world money for virtual goods

"July's report reveals that 75 percent of the respondents (a sample size of 2,221 respondents was polled) have used real-world money to pay for virtual goods, and that roughly half expect to continue to spend about the same amount of real-world cash over the next 12 months.
Additionally, women over the age of 25 are stepping up their games and spending more than everyone else. When looking at the median spent on first-party purchases within social-network games, the average female spent $55 dollars, compared to only $30 for males. Females also spent twice as much ($50 compared to $25) when comparing purchases of in-game currency and the median overall expenditure was higher for females than males, at $80 to $60, respectively."
Source:  Digital Goods Spending Report by VG Market and Playspan, reported by CNET, 21st July 2010