There's no average. It's just a target. You don't get $10/k a month overnight. It's a figure that you work toward. Many people don't need that much to live. It depends where you're at. If you need 5k/month to live then you can reach your goal even faster. $10k/month seemed like a good goal for the article that could support most people.
uh, okay. then you might want to update your blog before there are 1000s of unemployed web developers building their lifestyle web apps for eternal target of 10k/month.
so this 10k/month figure is averaged from how many years?