False. I will never understand why some people think you have to have that many sites to make good money from AdSense. If you weren't able to make good money with one real quality site, then you did something wrong.
Hell, my girlfriend makes money with one bad quality site.. and the few others she has are not much better graphically, but at least she makes the images herself.. I don't understand those who bought into the concept of having 100s sites each earning $1 a day.. Yes at the end of the day it makes the same good money, but why this route? It's a good route for selling the sites after a while, like if you have 100 sites earning $1 each and you manage to sell one at $3,000 the other at $2,000 then you still have many left and yes in that case it has an interest over having only a handful sites earnings each dozens $ each day. Like in real estate it may be better to have 20 small studio units than 2 big condos.. If you see websites as web properties, then ok it can make sense to have a lot of them for selling them after. But for adsense money, if you intend on keeping your sites for yourself for years, then no need to have more than half a dozen or so.. I don't like the idea of having only one big site, because we never know what can happen, like domain name theft, technical failure, etc.. in that case you find yourself with no revenue at all from one day to the next!
Just read this - not rich, but still shows that good money can be made off AdSense if you know what you're doing: http://www.johnchow.com/how-to-make-real-money-with-google-adsense
From my experience, It doesn't get me rich, yet. But it's enough for my tuition fees and my monthly expenses. It depends on how good niche of your website(s) are and how hard you try too. good luck.
There are people who earn WAY MORE than that. There's no limit, even 10k per month can be achieved. How? Hard work, dedication and LOTS OF TIME.. But it's certainly do-able if you don't get side-tracked chasing all the latest and greatest shiny red balls that cross your way.