Those Yahoo numbers are "Estimates" not actual numbers. It's just like when you hear that a star has an estimated worth of $40 million dollars. It's not that they have $40 mil in the bank at the moment but they have the "potential" to make $40 million dollars through the life of their career. But that's a big "but" because no one will know if they will still be popular in the future as they are now. Odds are, they probably won't
As for these Youtube stars their actual pay checks range from $1,000 - $2,500 a month. A decent salary but no more than someone with a college degree and an entry level job. Yeah they get money from the ad revenue but nobody clicks on the ads. Otherwise, Facebook would be making bank right now. Anyhow, you can tell that Youtubers don't make much because their surroundings are so middle class. They also post and make videos on a daily basis. I'm sure work that's a 80 hrs a week; brainstorming ideas, editing, directing, and promoting on Twitter/Youtube/Facebook/Answering Emails/IMs. So in the end they probably get paid #$3.12 - $7.81 - $10 per hour. So I would not envy any Youtube star.
They also rarely upgrade their filming equipment. Believe me if they were getting $100,000 and up, they would have far better production values. Or at the very least better clothes.
Don't get me wrong. They might get an extra $5,000 here or there, promoting some product but on the celebrity food chain they are the lowest of the low. Heck, people who star in lifetime movies make more money in one picture than Youtube stars make in a year.