Now unless you have a nice site full of some useful contents and a ultra huge amount of traffic, its always better not to depend too much on AdSense. But thats just my opinion.
So after read all reply post here,the point is 1 site can earn 300 a day as long as have good contents and tons traffic,that right guys?
for you guys that´s probably easy, but im Portugal the earnings are quite low, so... here´s an example: one word in US = 5.75 us dollars... the exact same word but in portuguese: 0.33 Euros... See the diference?
1 site can earn $5000 a day from Adsense if it has great content and tons of traffic. Depends what you call "tons" of traffic But yes, it is possible.
Many thread that I read on DP always said good contents and drive a lot traffic to your site is key to earn big buck from your site.